


Class 

Book 



I 

















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WAR DEPARTMENT :: OFFICE OF THE SURGEON GENERAL 


BULLETIN No. 6 


AUGUST, 1914 


THE PROPHYLAXIS OF MALARIA 
WITH SPECIAL REFERENCE TO 
THE MILITARY SERVICE 


BY 

CHARLES F. CRAIG 

Captain, Medical Corps, U. S. Army 



WASHINGTON 

GOVERNMENT PRINTING OFFICE 
1914 




















'•►a 


LIST OF BULLETINS* 

WAR DEPARTMENT* OFFICE OF THE SURGEON GENERAL. 

No. 1. Photomicrographs of Spirochetae, Entamebae, Plasmodia, Trypanosomes, 
Leishmania, Negri Bodies and Parasitic Helminths. January, 1913. 
No, 2. Papers by Officers of the Medical Corps, U. S. Army, read before the 
Fifteenth International Congress of Hygiene and Demography. Janu¬ 
ary, 1913. ; 

No. 3. Studies of Syphilis, by Charles F. Craig, Captain, Medical Corps, V. S. 

Army, and Henry J. Nichols, Captain, Medical Corps, U. S. Army, with 
Introduction by Major Frederick F. Russell, Medical Corps, U. S. 
Army. June, 1913. 

No. 4. Disease-Bearing Mosquitoes of North and Central America, the West 
Indies, and the Philippine Islands, by C. S. Ludlow, Ph. D., Anatomist, 
Army Medical Museum. November, 1913, • / 

No. 5. Mental Disease and Defect in the U. S. Troops, by Captain Edgar King, 
Medical Corps, United States Army. March, 1914. 


WAR DEPARTMENT :: OFFICE OF THE SURGEON GENERAL 


BULLETIN No. 6 


AUGUST, 1914 


L|,S, M&oIa e,'^ \ c\eWU 


THE PROPHYLAXIS OF MALARIA 
WITH SPECIAL REFERENCE TO 
THE MILITARY SERVICE 



CHARLES F. CRAIG 

Captain, Medical Corps, U. S. Army 


PUBLISHED BY AUTHORITY OF THE ACT OF CON¬ 
GRESS APPROVED AUGUST 1, 1914, AND WITH 
THE APPROVAL OF THE SECRETARY OF WAR, 
FOR THE INFORMATION OF MEDICAL OFFICERS 



WASHINGTON 

GOVERNMENT PRINTING OFFICE 
1914 














V' 



\ 


f% OF D. 

DEC 8 1914 



PREFACE. 


In the sundry civil act tor 1914, under the appropriation for 
printing and binding for the War Department, it was provided: 

That the sum of $3,000, or so much thereof as may be necessary, may be 
used for the publication from time to time of bulletins prepared under the 
direction of the Surgeon General of the Army, for the information of medical 
officers, when approved by the Secretary of War. 

Similar provision was made in the sundry civil act for 1915, and 
it is hoped that this appropriation will be continued from year to 
year in the future. It is intended that these bulletins shall be used 
for the publication to the Medical Corps of the special technical 
work of the service laboratories, the reports of the boards for the 
study of tropical diseases, and other work of medical officers which 
is of too special or technical a character to make it acceptable for 
publication in the medical journals and the Military Surgeon. 

The bulletin will be published, if possible, at least quarterly. 
Officers of the corps are requested to submit suitable articles to this 
office for use in the bulletin, with the understanding that they may 
be published elsewhere by the author if found not suitable for the 
bulletin. 

'i • .* William C. Gorgas, 
Surgeon General ', United States Army. 

September 24, 1913. 

ORDER. 

A board of officers of the Medical Corps, representing the Sanitary 
and Statistical Division and the Library of the Surgeon GeneraTs 
Office and the Laboratory of the Army Medical School, is hereby 
convened for the purpose of collecting materials and arranging for 
the publication of the bulletins for the instruction of medical officers 
authorized by the act approved June 23. 1913. 

Detail for the board : 

Lieut. Col. Champe C. McCulloch, jr- 
Maj. William J. L. Lyster. 

Maj . Eugene B. Whitmore. 

By order of the Surgeon General: 

Chas. M. Gandy, 

Lieutenant Colonel , Medical Corps , United States Army. 

































































































































TABLE OF CONTENTS. 

Page. 

Introductory Remarks. 9 

Illustrations of successful malaria prophylaxis. 10 

Results in the Army.;. 10 

Chapter I. The malaria plasmodia. 17 

Methods of demonstrating the plasmodia. 17 

Apparatus. 17 

Living specimens. 17 

Stained specimens. 18 

Method of staining. 18 

Staining reactions. 20 

Ross thick film method. 20 

Morphology and life cycle. 21 

Classification. 21 

Plasmodium vivax. 22 

Unstained specimens. 22 

Stained specimens. 23 

Plasmodium malariae. 24 

Unstained specimens. 24 

Stained specimens. 25 

Plasmodium falciparum. 26 

Unstained specimens. 26 

Stained specimens. 27 

Plasmodium falciparum quotidianum. 27 

Living specimens. 27 

Stained specimens. 28 

Development of plasmodia in the mosquito. 28 

Morphology of the sexual forms of the plasmodia. 30 

Gametes of Plasmodium vivax. 31 

Gametes of Plasmodium malariae. 34 

Gametes of aestivo-autumnal plasmodia. 34 

Differential diagnosis of the malarial plasmodia. 36 

Objects which may be mistaken for the plasmodia. 37 

In fresh blood. 38 

In stained preparations. 39 

Chapter II. The malaria mosquitoes. 41 

Geographical distribution. 41 

Number of infected mosquitoes. 42 

Species of mosquito in relation to malaria. 43 

Classification. 42 

External anatomy. 44 

Internal anatomy. 45 

Life cycle of anophelines. 46 

The ova. 46 

The larvae. 47 

The pupae. 48 

The adult mosquito. 48 

5 
















































6 


\ 

CONTENTS. 

Chapter II. The malaria mosquitoes—Continued. 

Habits. 48 

Of the larvae. 48 

Of adults. 48 

Feeding. 48 

Time of day of biting. 49 

Flying distance. 50 

Breeding places. 51 

Color in relation to anophelines. 52 

Longevity and hibernation... 52 

Number of generations. 53 

Resting position of adults. 53 

Practical points in the differentiation of the anophelinse. 54 

Methods of collecting and dissecting mosquitoes. 55 

Dissection of the salivary glands. 56 

Dissection of the “stomach”. 57 

Chapter III. Prophylactic methods based upon the destruction of malaria 

mosquitoes. 58 

General remarks. 58 

Drainage. 59 

The blind drain. 59 

The cement-lined open drain. 60 

Subsoil drainage with tiles. 60 

Filling. 60 

Removal of shelter. 60 

Larvicides. 61 

Kerosene (fuel oil). 61 

Canal Zone larvicide. 63 

Other larvicides. 64 

Destruction of larvae by fish. 64 

Abolition of breeding places about barracks and quarters. 65 

Destruction of the adult mosquito. 67 

Sulphur dioxide. 67 

Smudges. 68 

Pyrethrum powder. 68 

Other fumigants. 68 

Mosquito catching as a prophylactic method. 68 

Chapter IV. Prophylactic methods based upon the protection of man from the 

bites of mosquitoes. 72 

General remarks.:. 72 

Screening. 72 

Selection of screening material. 73 

Size of the mesh. . 73 

Method of screening. 75 

Mosquito nets. 75 

Head nets and gloves. 76 

Use of odorous substances on the skin. 76 

Results of screening. 77 

Screening of malarial patients. 78 

Chapter V. Prophylactic methods based upon the destruction of malaria 

plasmodia (quinine prophylaxis). 80 

General remarks. 80 

Action of quinine upon the plasmodia. 82 

Form of quinine to be used in prophylaxis. 84 




















































CONTENTS. 7 

Chapter V.—Prophylactic methods, etc.—Continued. 

Methods of administration and dosage. 86 

Celli’s method. 86 

Sergent’s method. 86 

Zieman and Noclit’s method. 86 

Plehn’s method. 86 

Koch’s method. 86 

Service method. 86 

Quinine-fast strains of plasmodia. 87 

Treatment of infections and “carriers”. 88 

Discovery and treatment of latent infections, i. 89 

Proportion of latent infections. 90 

Methods of diagnosing latent infections. 94 

Treatment of latent infections. 94 

Discovery of gamete carriers. 96 

Time of occurrence of gametes. 97 

Percentage of individuals showing gametes. 97 

Estimation of number of gametes in prophylaxis. 98 

Effect of quinine upon gametes. 99 

Treatment of gamete carriers in prophylaxis. 99 

Treatment of initial and recurrent infections in prophylaxis. 100 

Results of quinine prophylaxis. 103 

Chapter VI. The application of the methods of malarial prophylaxis to the 

military service. 107 

General remarks. 107 

Malaria prophylaxis in the field. 107 

Malaria prophylaxis in semipermanent camps. 108 

Malaria prophylaxis in permanent posts. 109 

References. 113 


























































































' 










































THE PROPHYLAXIS OF MALARIA. 


INTRODUCTORY REMARKS. 

The discovery by Laveran of the parasites concerned in the etiology 
of the malarial fevers, and by Ross of the method of transmission of 
these parasites from man to man by the mosquito, has placed the 
prophylaxis of these infections upon a firm scientific basis; while the 
discovery of cinchona and its alkaloid, quinine, placed in our hands 
a true specific against the parasites. In many countries these dis¬ 
coveries have been taken advantage of in extensive campaigns against 
malaria, and such campaigns have been successful in proportion to 
the thoroughness with which measures based upon etiological facts 
have been applied in prophylaxis. 

In this bulletin, prepared at the request of the editorial board 
appointed by the Surgeon General of the Army, special stress will be 
laid upon those measures that are most applicable in the prophylaxis 
of malaria in the military service, including service in the field as 
well as in semipermanent camps and permanent posts. It is obvious 
that methods of prophylaxis that would he suitable in a permanent 
post might be impracticable upon the march, in bivouac, and in 
camps lasting only a day or two, so that it will be necessary to con¬ 
sider somewhat in extenso the prophylactic measures suitable under 
the special conditions brought about by military operations as well 
as those suited to preventing infection in permanent posts. 

At the present time our knowledge of the etiology of malarial in¬ 
fections is so extensive and accurate that no matter how badly a 
region may be infected or how difficult the local conditions may 
make the application of prophylactic measures some method may 
be adopted that will result in success. It is now proven beyond con- 
troversv that the malarial fevers are transmitted from man to man 
by mosquitoes belonging to the Anophelince; that these mosquitoes 
in order to become infective must have bitten an infected individual; 
that the malaria parasites undergo a definite cycle of development 
in both man and the mosquito, which, if interrupted at any stage, 
will result in the death of the parasites; and that these parasites, so 
far as we know, exist only in man and mosquitoes, so that it is 
unnecessary to consider other animal or insect hosts in the prophy¬ 
laxis of malaria. Therefore it follows that if it were possible to 
destroy all malaria-carrying mosquitoes or kill all the plasmodia 
in the blood of all infected individuals we would succeed in the 


9 


10 


PROPHYLAXIS OF MALARIA. 


eradication of these fevers in every locality. Unfortunately, we 
must admit that in practice we can only hope for a partial success 
if we depend upon one method of prophylaxis alone, and it is gen¬ 
erally necessary to combine methods looking to the destruction of 
mosquitoes, the protection of man from the bites of these insects, and 
the destruction of the malaria plasmodia. 

That methods based upon the discoveries of Laveran and Koss, 
when properly applied, are successful has been proven by numerous 
sanitarians. The success achieved by Gen. Gorgas and Col. Kean, 
of the Medical Corps, in Habana; of Gen. Gorgas in the Canal Zone; 
of Celli in Italy; of Watson in the Federated Malay States; and of 
the Sergents in Algeria in the prevention of malaria has demon¬ 
strated for all time the wonderful value of prophylactic measures 
against these infections, and there is no more striking illustration 
of what may be expected from intelligent prophylaxis than is shown 
in Chart No. I, giving the malarial rates in the Canal Zone since 
1906 to 1913. As will be noted, during 1906 nearly T per cent of the 
entire working force on the canal entered hospital each month suf¬ 
fering from malarial infections, while in 1912 less than 1 per cent 
per month entered hospital from these infections. 

In the Army there has been a gradual and continued reduction in 
the number of cases of malaria since 1898, as shown by Chart No. II. 
It should be understood, however, that the enormous number of 
admissions from malarial fevers in 1898, 1899, and even in 1900, as 
shown in this chart, can not be taken as representing the actual 
facts, for it is well known that a very large percentage of the cases 
of typhoid fever occurring during these years, and especially during 
1898 and 1899, were diagnosed as remittent malarial fever and so 
entered upon the records. However, if Ave accept the year 1901 
as representing accurate statistics of this disease, it will be noted 
that the admission rate for all American troops, serving both at 
home and in our tropical possessions, has been reduced from 365.39 
per 1,000, the rate for 1901, to 24.75 per 1,000, the rate for 1913. 

The noneffective rate from malarial infections, the best index 
we possess of the influence of the disease upon the efficiency of the 
Army, has likewise fallen greatly. This rate for all American 
troops, as shown in Chart III, serving both at home and abroad, 
Avas 4.46 in 1903, while in 1913 it was only 0.53, the loAvest noneffec¬ 
tive rate from these feA^ers since 1898. 

In the troops serving in the United States the reduction in 
malaria, as would be expected, has been more marked than in the 
Philippines. In Chart No. IV is given the admission and non- 
effective rates for these fevers since 1904, and it will be noted that 
there has been a steady decrease in both rates, until in 1913 we 


Chart No. 1. 



i 

to 

3 

3 

7 

6 

S 

4- 

3 

2 

/ 

0 


58000—14°. (To face page 10.) 


















































































































































































































































































































































(Mp • *• 















PROPHYLAXIS OF MALARIA. 


11 


Chart No. II. 


<7 /#r/<?/ /Evers'. 

^ 7 c)fn /s S'/ O n. 7?c? -t e ^ . 

?~c? f e-s - f /&r/c?/ /^ere^ ^ A 

^^rer/co'^ -Z^oo/c J'|e^?//Jz t e9 &/-%. / 


y<z#rs 


ffdm/ SS/OK 

7? 3 -£gs 


O /oo. 2 oo, Jo o', ft-oo. So o. £oo. 


/^^S> 




/??? 


633JV 


/?o o 


5Z3./7 


/?Q / 


3 6 S3? 


/?oZ 


279:63 


/?o3 


/ 76.03 


/?o9 


89-36 


/7°3- 


3 33S 


/?o6 


/ 0 7-67 


/?o7 


63/0 


/?° 8 


96.33 


/?°7 


3 8.7Z 


/f/o 


2 8,99 


/y// 


Z3./8 


/y/z 


90.00 


/?/3 


Z 9,7S 


















































































































































































12 


PROPHYLAXIS OF MALARIA. 


Chart No. III. 


e /<? r/<? / /sKerj'. 
e //& c *vV e 


^sfoot c/f e c t'/re 7" for /<??•/<? / /ere^x -z^ e 

ffn e r/ c^-n. ^ r ocyo s f *i /ss fee* e -n ^y e ? r S f /fc3— /f/3. 



























































PROPHYLAXIS OF MALARIA. 


13 


reached the very small noneffective rate of 0.18 and the admission 
rate of 8.79. In the Philippines on the other hand (Chart No. V) 
the decrease has not been as steady, and in 1912 and 1913 the ad¬ 
mission rates are higher than in 1910 or 1911. The exact reason for 
this increase during the years mentioned is not known but it was 
probably due to more exposure in the field because of local maneuvers 
or expeditions. 

The decrease of malaria in the Army has been brought about 
largely by measures directed against the mosquitoes transmitting 
the disease, and the protection of man from the bites of these insects. 
Quinine prophylaxis has probably had but little to do with this re¬ 
duction, as the use of this method has been very limited. Neither 
has the control of treatment by microscopic examinations of the 
blood and the treatment of “ carriers " and latent infections operated 
to any extent in reducing the disease in the Army, as these methods 
have been very little used, and it is believed that had these methods 
been widely employed the reduction of malaria would have been 
much more marked and much more rapid than it has been. 

The methods of prophylaxis adopted in different localities must 
vary with the peculiar conditions present in each region, and com¬ 
mon sense must be used here as in every other procedure for the 
prevention of disease. High-flown theories must give place to a 
calm study of the situation and the means most applicable and best 
adapted to fighting the infection. Under some conditions we may 
be able to practically eradicate mosquitoes, while under others this 
measure may be impossible, and quinine prophylaxis will have to be 
substituted, together with measures for the protection of man from 
the bites of mosquitoes. In many, if not most, localities the best 
results will be secured by the combination of several prophylactic 


measures, and I am not at all in sympathy with those who insist that 
•either upon the destruction of mosquitoes or the prophylactic use of 
quinine alone we must depend for success in the prevention of the 
malarial fevers. 

The prophylaxis of malaria, to be successful, must rest upon a 
thorough knowledge of the etiolog}^ of these infections. In the past 
much effort has been wasted and money uselessly expended in fool¬ 
ish attempts at prophylaxis by individuals possessing a very super¬ 
ficial knowledge of either the parasites causing the disease or the 
insects transmitting the infection, and most of the unfavorable re¬ 
ports regarding various methods of prophylaxis, if carefully studied, 
will be found to be based upon insufficient evidence furnished by 
those unacquainted with the real facts regarding the etiology of 
malaria. 

A knowledge of the morphology and life cycle of the parasites 
causing malaria and of the mosquitoes transmitting the disease is 


14 


PROPHYLAXIS OP MALARIA. 


Chart No. IV. 


^/9Qs 7Z/£S/oft ej/y*ec-f/yc 

e//e ct*/ k e r&tes -/^o r X 

/J^ery^/ory/e 1 &?e/-£ed gs, ers c <^>*. /p~oayO »? 

^e*i//ST?<='d #t e*t}^ye&rG, /fO *X —/ 



J%)?n/ ss/on r&tes, yfoneffectiye r<Jles 


































































































































































PROPHYLAXIS OF MALARIA. 


15 


Chart No. V. 


/^e vers. 

^/ : /3'7?t/ss/ort 'Tx’j-tes. 
sss/on. p-^-^es jfor- /<?r/< 7//^yers y 20 *- 

T^A//s/>y/n <? JTs/?*td&, c&*t~~7rooy>& we/rj 

yezrs, /yoy—/y / 3. 


X 


e#rs 


es. 


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0 

/ 

s~ 

z 

0 

z 

3 

0 

0 

0 

0 

0 

0 


/?o ^ 


Z Z 0.6 


/yos'z 6 /.«r. 


//<? 


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/ ^ 7 :r 7 


/ ?oz 


/ 2 3 .?- 


/ fO ? 


/ / Z, 3 S 


/?/ ° 


8 6.3 y, 


/?/ / 


r r.z c 


/ ?/z 


/ 7 / 00 


/f /3 


/ / z.oz 












































































































































16 


PROPHYLAXIS OF MALARIA. 


absolutely essential to one who hopes to achieve success in prophy¬ 
laxis. This does not mean that one must be a professional protozo¬ 
ologist or entomologist, for a good working knowledge of these sub¬ 
jects may be obtained from the careful study of the blood from a 
few cases of malaria and from the investigation of the structure and 
habits of a few species of mosquitoes. One should be able to recog¬ 
nize the various forms of the malaria plasmodia occurring in the 
blood of man and also be able to differentiate mosquitoes belonging to 
the Anophelina ? from other mosquitoes, and, fortunately, this knowl¬ 
edge may be easily acquired by anyone who has access to the neces¬ 
sary material. 

As the first step in any successful attempt at the prophylaxis of 
malaria is the diagnosis of the presence of infection either in man or 
the mosquito, it is necessary to consider as briefly as is consistent 
with the importance of the subject the methods of demonstrating the 
parasites and their morphology and life cycle. The discovery of 
“ carriers v of the infection, so important from a prophylactic stand¬ 
point, and the proper treatment of all malarial disease, depends upon 
the recognition of the plasmodia in the blood of man, while no mala¬ 
ria survey can be called complete which does not include the demon¬ 
stration of the plasmodia within the mosquitoes of the locality in¬ 
vestigated. In the following sections dealing with the plasmodia and 
the mosquitoes transmitting them I have endeavored to give the facts 
that are most essential to one working along the line of prophylaxis; 
and while it has been necessary to describe the morphology of the 
plasmodia I have limited myself as much as possible in the descrip¬ 
tion, placing special emphasis upon the forms of the plasmodia that 
infect the mosquito and that may also be demonstrated in the blood 
of man, i. e., the gametes. No attempt has been made to describe in 
detail the anatomy of mosquitoes, but special attention has been paid 
to the broad points differentiating the Anophelinai from other mos¬ 
quitoes and to the habits of certain species transmitting the malarial 
fevers. The methods of demonstrating the plasmodia are those that 
I have found most useful and can be easily applied by anyone hav¬ 
ing a knowledge of the microscope and of microscopical technique. 

Fort Leavenworth, Kansas, 

July, 191 


Chapter I. 


THE MALARIA PLASMODIA. 

Methods of demonstrating the plasmodia. —The parasites causing 
the malarial fevers may be studied in either the living condition or 
in stained preparations of blood. For the military surgeon the 
examination of the fresh blood is of special value, for staining solu¬ 
tions will not always be at hand, and it is most unfortunate, from 
a military standpoint, that the study of the living plasmodia in 
fresh blood has been so entirely replaced by the use of stained prepa¬ 
rations. While, at permanent posts and base hospitals, where stain¬ 
ing solutions .can be prepared and used, the stained preparations of 
blood are to be preferred, every military surgeon should be familiar 
with the appearance of the plasmodia in fresh blood, for in the field 
the examination of unstained specimens will be found the most prac¬ 
ticable and rapid method of diagnosing malarial infections. Where 
stained preparations can be made, however, they possess the great 
advantage that the plasmodia are more easily seen and are less 
liable to be mistaken for other objects that may be present in the 
specimens examined. 

Apparatus. —The apparatus necessary in making a blood examina¬ 
tion for malaria is so very simple, occupies so little space, and is so 
easily transported, that there is no excuse for its absence even in 
military operations in the field. A good compound microscope pro¬ 
vided with a one-twelfth oil immersion lens, a bottle of immersion 
oil, microscopic slides and cover-glasses, two or three medicine drop¬ 
pers, a bottle of staining solution, and boiled or distilled water are 
all that is necessary to make the most exact examination of the blood 
for malaria. In operations in the field the bottles of staining solu¬ 
tion and distilled water could be omitted, the diagnosis of infection 
being made from the examination of fresh specimens of blood. The 
one-twelfth oil immersion lens is absolutely essential, for while the 
larger forms of the tertian and quartan plasmodia and the gametes , 
or crescents, of the aestivo-autumnal fevers may be seen with lower 
power lenses, the small, hyalin ring-forms can only be well seen 
when the one-twelfth lens is used. 

Preparation of living specimens. —The following procedure is rec¬ 
ommended if it is desired to procure fresh specimens of blood for 
examination for the plasmodia. The patient’s ear lobe or the tip of 
the finger is carefully cleaned with alcohol, dried thoroughly, a 

17 


58000°—14-2 



18 


PROPHYLAXIS OF MALARIA. 


slight puncture made with a lancet or needle, and the first drop or 
two of blood allowed to flow away. A very small drop is then taken 
upon the center of a microscopic slide which has been carefully 
cleaned and a cover glass placed gently over it. If the slide is clean 
and the drop of blood small the weight of the cover glass will cause 
the blood to spread evenly and quickly beneath it; but if it does not, 
very slight pressure will suffice to spread the blood and will do no 
harm. If upon examination it is found that the blood cells are in 
clumps or rouleaux, the preparation should be discarded and one 
prepared in which the red cells are spread singly and eventy over 
the microscopic field. The preparations should be examined as soon 
as possible-; but if carefully wrapped in tissue paper, they may be 
carried in the pocket for several hours without much danger of 
changes occurring which will obscure the plasmodia; and if the 
specimens be carefully ringed with vaseline, they will keep for as 
long as 12 hours. The ear is preferable to the finger for obtaining 
blood, especially in children, as there is less pain and the patient can 
not watch the operator during the procedure. At least a half hour 
should be spent upon the examination of the specimen before a 
negative report is returned, and at least three or four preparations 
should be examined. In the vast majority of active infections, how¬ 
ever, a few moments examination will disclose the plasmodia, but 
where a search is being made for latent infections and “ carriers ” 
it is not safe to consider a case as negative unless several speci¬ 
mens are carefully examined. 

Preparation of stained specimens .—All that is necessary in the 
way of apparatus for preparing blood smears for staining are micro¬ 
scopic slides and a needle with which to make the puncture in the 
ear-lobe or finger. After cleansing the ear or finger, as described, a 
puncture is made with the needle and a small drop of blood caught 
upon the surface of a clean microscopic slide, near one end; as 
quickly as possible the end of another slide is placed in contact with 
the drop of blood, either before or behind it, and the blood alloAved 
to spread along the edge of the applied end. As soon as this occurs 
the upper or applied slide is. pushed or drawn gently along the 
surface of the slide containing the drop of blood, and when this is 
properly done a thin even smear is obtained. Several smears should 
be prepared from each individual examined. 

Method of staining .—Many methods have been devised for stain¬ 
ing the malaria plasmodia, but I have found Wright’s modification 
of the Eomanowsky stain as satisfactory as any, and it is absolutely 
reliable when the staining solution is properly prepared and used. 
Considerable time and care are necessary in the preparation of the 
stain, and this has been urged as an objection to its use, but anyone 
who will carefully follow the directions that follow will have no 


PROPHYLAXIS OF MALARIA. 


19 


trouble in securing a reliable stain, and, in time of active field opera¬ 
tions, if it were desired to issue the powder, it could be prepared in 
large amounts at the various department laboratories and issued in 
sealed glass tubes, each tube containing enough powder for a definite 
amount of staining solution, and with the powder could be sent 
enough of the proper methylic alcohol to make up the amount of solu¬ 
tion indicated. 

The powder used in preparing the staining solution is obtained as 
follows: In a flask add 0.5 gram of c. p. sodium bicarbonate to 100 
c. c. of distilled water; dissolve thoroughly, and slowly add, while 
shaking, 1 gram of Grubler's methylene blue; heat for one hour in 
an Arnold sterilizer after the steam is up, and then cool the solution. 
A considerable amount of the methvlene blue will remain undis- 
solved, but this should be allowed to remain in the solution. 

Make a solution of Grubler's yellow aqueous eosin by adding 1 
gram of eosin to 1,000 grams of distilled water. Add this slowly, 
while stirring, to the cooled methylene blue solution which has been 
poured into a white dish or bowl. The eosin solution is added until 
a well-marked precipitate appears and the surface of the mixture is 
covered with a greenish metallic scum. Test repeatedly, while add¬ 
ing the eosin solution, by placing a drop of the mixture upon a piece 
of white filter paper. When sufficient of the eosin solution has been 
added a well-marked pink halo should surround the small amount of 
blue precipitate left upon the paper. Now allow the mixture to stand 
for 15 minutes and then filter through one small filter paper; the 
precipitate is saved, dried in a hot-air oven at 60° C., the greenish 
mass thus obtained powdered, and stored in an air-tight bottle. Large 
amounts of the powder may be prepared by increasing the amounts 
of the reagents given, in proper ratio. 

The staining solution .—The solution used in staining the blood 
smears is prepared by taking 0.3 gram of the powder and adding it 
to 100 c. c. of pure methylic alcohol (this must be Merck’s reagent 
alcohol) filter, and add enough alcohol to bring the entire amount to 
the original 100 c. c. Let stand for an hour or two before using. 

Method of use .—Add a few drops of the staining solution to the 
blood smear and let stand for from three to five minutes. This fixes 
the specimen. Then add enough distilled water to cause a slight 
greenish metallic scum to form upon the surface of the solution; let 
stand for five minutes, wash in running distilled water, and examine 
when dry. The exact time for staining, after the addition of the 
distilled water, varies somewhat with different specimens of blood, 
but a little experience will soon enable one to judge the right time. 

The final washing with distilled water is very important, as by it 
the precipitate formed during the staining process is removed and 
the differentiation of the staining of the cytoplasm of the erythrocyte 


20 


PROPHYLAXIS OF MALARIA. 


and the chromatin of the plasmodia is obtained. The washing should 
be continued until the specimen becomes a delicate shade of pink or 
pinkish-brown. If distilled water can not be obtained, thoroughly 
boiled water may be used instead. 

Staining reactions with Wright's stain .—In specimens of blood 
properly stained with Wright’s stain, the red blood corpuscles are 
stained a brownish-pink or light salmon, while the various leucocytes 
are stained as follows: The polynuclear leucocytes present a violet 
nucleus with unstained cytoplasm except for light pink granules; 
the mononuclears and lymphocytes have a dark ruby-red or violet 
nucleus, while the cytoplasm is stained blue: the eosinophiles have 
a violet or bluish-violet nucleus, while the granules are stained red; 
the mast cells have purplish-black granules and a dark violet nu¬ 
cleus; while the blood plates stain a ruby-red color, with, in most 
instances, a more or less definite pale lilac margin. 

The cytoplasm of the malaria plasmodia stains a robin's egg 
blue, the vesicular portion of the nucleus remains unstained, while 
the chromatin of the nucleus stains a rubv-red or brilliant violet 
color. The pigment generally appears greenish in color in the ter¬ 
tian plasmodia and almost black in the quartan and estivo-autumnal 
plasmodia. 

The Ross thick-film method .—In suspected cases of malaria in 
which the plasmodia can not be demonstrated by the methods de¬ 
scribed, the thick-film method of Koss should be tried. This method 
will be found of special service in the search for “carriers” of the 
infection and should always be employed in a malaria survey be¬ 
fore a localitv is returned as free from the disease. 

A large drop of blood is placed upon a microscopic slide at or 
near the middle, and is spread with a needle until it covers an area 
about one-half inch in diameter. The smearing may be done with a 
platinum loop, and the film should be made as evenly as possible. 
The preparation is now placed aside and allowed to dry. 

After the film is dry, the slide is placed in a mixture composed 
of 50 c. c. of commercial ethyl alcohol containing 10 drops of com¬ 
mercial hydrochloric acid, and removed when the hemoglobin is 
completely dissolved—a process which is usually complete in from 
10 minutes to half an hour, varying with the thickness of the blood 
smear. The preparation is now fixed and should be washed in run¬ 
ning water for 15 minutes in order to remove the acid, which en¬ 
tirely prevents staining if any considerable amount remains upon 
the slide. After washing, the specimen is allowed to dry and stained 
with Wright’s stain in the manner already described. More stain 
should be used in covering the film, and a longer time should be 
allowed for staining because of the thickness of the film of blood. 


PROPHYLAXIS OF MALARIA. 


21 


After staining, the preparation is washed in running tap water until 
no more blue color comes from the film. The specimen is then al¬ 
lowed to dry, after which it is ready for examination. 

In specimens stained in this manner it should be remembered 
that, owing to the dissolving of the hemoglobin by the acid, the 
cytoplasm of the red blood corpuscles is not distinctly stained, the 
intracellular plasmodia appearing to be free in the plasma. The 
entire film is more or less pink in color, the plasmodia appearing 
as blue bodies containing more or less red chromatin against the 
pinkish background. The tertian and quartan plasmodia, if beyond 
the ring stage in growth, appear as irregular blue masses containing 
granules of red chromatin, while the ring forms appear as blue rings 
containing one or two red chromatin granules, or as minute, irregu¬ 
lar bodies, if viewed at an angle. The gametes are easily distin¬ 
guished, although the crescentic gamete of the estivo-autumnal plas¬ 
modia often appears distorted. Some experience is required to 
identify the plasmodia in these thick films, but a little practice will 
soon enable one to become expert in the use of this very valuable 
method of demonstrating the malaria plasmodia. 

THE MORPHOLOGY AND LIFE CYCLE OF THE MALARIA 

PLASMODIA. 

The malaria plasmodia were first described by Laver an 3 in 1880 
and are found in man upon and within the red blood corpuscles. In 
this situation they feed upon and destroy the corpuscles, producing 
thus the anaemia always present in every malarial infection, and 
by their sporulation the symptom complex which we know as the 
malarial paroxysm. Although the classification of these parasites 
has occupied the attention of zoologists for years, it can not be said 
that there is yet a complete agreement regarding the exact position 
of the species causing malaria in man. All are agreed that they 
belong to the Protozoa, and most authorities place them in the 
Sporozoa , and in the order Ilcemosporidia. At least three species are 
recognized by the vast majority of observers—i. e., Plasmodium 
vivax (the tertian parasite), Plasmodium malariae (the quartan 
parasite), and Plasmodium falciparum (the estivo-autumnal para¬ 
site). The latter species has been divided by many observers into 
two varieties, the tertian estivo-autumnal plasmodium and the quo¬ 
tidian estivo-autumnal plasmodium. The tertian species should 
be called Plasmodium falciparum , while 1 4 have proposed the name 
Plasmodium falciparum guotidianum for the parasite causing the 
quotidian type of estivo-autumnal malaria, believing it to be a 
subspecies of Plasmodium falciparum. 


22 


PROPHYLAXIS OF MALARIA. 


In describing the malaria plasmodia two distinct life cycles must 
be considered—first, the human or asexual cycle, called schizogony , 
occurring in man; and second, the mosquito or sexual cycle, called 
sporogony , occurring in the infected mosquito. In each of these 
cycles of development the morphology of the parasites varies greatly 
and should be familiar to everyone engaged in the prophylaxis of the 
malarial fevers. 

In the following descriptions the morphology of the various spe¬ 
cies of human plasmodia will be first given as observed in living 
preparations and then as observed in stained preparations. The 
forms pertaining to the human cycle of development will first be 
described and then the forms concerned in the mosquito cycle. 

Morphology of Plasmodium vivax (the tertian parasite) ( Schi¬ 
zogony or human cycle. —As is well known this species of malaria 
plasmodium completes its cycle of development in the blood of man 
in 48 hours and produces the well-known type of malarial fever 
associated with a chill and fever occurring every other day. 

The parasite is first observed, in unstained preparations, within 
or upon the red blood corpuscle as a small, nonmotile, hyaline ring 
or disk, the trophozoite , measuring about 2 microns in diameter; its 
outline is very indistinct, and it is often overlooked owing to lack 
of amoeboid movement and the delicate veil-like consistency of its 
cytoplasm. As it grows older, becoming the schizont , it develops 
marked amoeboid movement, but is still indistinct in outline until 
pigment is developed at the end of from six to eight hours. The 
pigment is reddish brown in color and arranged irregularly through¬ 
out the cytoplasm in the form of very fine granules. As development 
proceeds the pigment becomes motile, due apparently to currents 
within the cytoplasm of the parasite, while the amoeboid motion of 
the plasmodium becomes less pronounced. As growth proceeds the 
pigment increases gradually in amount and remains active until 
just before sporulation when it becomes collected in large masses or 
a single large irregular mass near the center of the parasite. 

At the end of 24 hours the plasmodium fills more than half of the 
infected red corpuscle, contains much actively motile pigment, and 
varies greatly in shape due to the marked amoeboid activity of the 
organism. The infected red cell is considerably larger than normal 
and lighter green in color. At the end of 36 hours the plasmodium 
has attained its greatest size and practically fills the infected cor¬ 
puscle. Amoeboid motion is sluggish, but the pigment, which has 
still further increased in amount, is very actively motile and is dis¬ 
tributed in the form of fine granules throughout the cytoplasm. The 
cytoplasm of the plasmodium is colorless, but the organism is sharply 
outlined. The infected red corpuscle is almost twice the size of the 
normal corpuscles surrounding it. At the end of 48 hours sporula- 


PROPHYLAXIS OF MALARIA. 


23 


tion occurs; the pigment becomes collected near the center or to one 
side of the plasmodium in the form of a compact clump or clumps, 
and fine radial striations are observed extending from the center 
toward the periphery of the plasmodium, dividing it into several 
ovoid segments or spores. As a rule, these spores, in the tertian 
plasmodium, are arranged in two rows, one row surrounding the 
center of the plasmodium and another surrounding the first row; 
but often the spores are arranged irregularly and are always devoid 
of pigment. They vary in number from 12 to 24, or even more, but 
the average is from 16 to 20. The spores are known as merozoites 
and when free in the blood plasma measure from one-fifth to 2 mi¬ 
crons in diameter, are oval in shape, hyaline in appearance, and 
present a spherical, refractive center, and a less refractive mass of 
protoplasm surround it. The merozoites are capable of infecting the 
red blood corpuscles and thus the human life cycle of the plasmo¬ 
dium is continued. 


EXPLANATION OF PLATE 1. 

Figure 1.— Plasmodium , vivax. (Tertian plasmodium.) Young forms or tlie 
so-called “ring forms.” Wright’s stain. X 1200. 

Figure 2. —Plasmodium vivax. Quarter-grown parasite. Wright’s stain. X 1200. 

Figure 3.— Plasmodium -vivax. Half-grown parasite. Wright’s stain. X 1500. 

Figure 4.— Plasmodium vivax. Three-quarters-grown parasite. Wright’s stain. 
X 1S00. 

EXPLANATION OF PLATE 2. 

Figure 1.— Plasmodium vivax. (Tertian plasmodium.) Pre-sporulating para¬ 
site. Wright’s stain. X 1800. 

Figure 2.— Plasmodium vivax. Sporulating parasite. Wright’s stain. X 1200. 

Figure 3.— Plasmodium vivax. Sporulating parasite. Wright’s stain. X 1800. 

Figure 4.— Plasmodium vivax. Sporulating parasite. Wright’s stain. X 1800. 

EXPLANATION OF PLATE 3. 

Figure 1.— Plasmodium vivax. (Tertian plasmodium.) Free spores or mero¬ 
zoites. Wright’s stain. X 1200. 

Figure 2.— Plasmodium vivax. Fully developed macrogametocyte of Plasmo¬ 
dium vivax. X 1800. 

Figure 3. — Plasmodium vivax. Fully developed micro gametocyte of Plasmo¬ 
dium vivax. Wright’s stain. X 1800. 

Figure 4. —Plasmodium vivax. Atypical parasite, resembling the parthenoge- 
nctic macrogametes described by Schaudinn. Wright’s stain. 
X 1500. 


In preparations stained with Wright’s stain, the youngest form 
of Plasmodium vivax appears in the red cell as the so-called “ ring 
form*' consisting of a delicate ring of cytoplasm stained a robin’s- 
egg blue, at one portion of which is a ruby-red dot of chromatin, the 
ring inclosing an unstained area through which the salmon or pink 
of the corpuscle is visible. In those plasmodia in which ameboid 


24 


PROPHYLAXIS OF MALARIA. 


motility was present at the time of fixation many irregular forms, of 
the “ring*’ are observed, due to minute pseudopodia arising from 
the periphery of the organism. Delicate, blue-stained filaments of 
cytoplasm may be observed spreading over the infected erythrocyte 
and the chromatin mass may be situated at any portion of the para¬ 
site, quite often within one of the pseudopodia. As the schizont 
becomes larger the blue-stained cytoplasm is observed to contain 
greenish pigment and the single dot of chromatin has increased 
until the cytoplasm contains threads and granules of this substance 
stained a brilliant red. At a certain period of development the 
chromatin divides into such fine filaments and grains that in the 
stained preparations the parasites at this stage appear to be almost 
devoid of this substance but prolonged staining will generally 
demonstrate a collection of very fine chromatin crannies inclosed 
within an unstained area, the vesicular portion of the nucleus. As 
sporulation approaches the cytoplasm stains more intensely blue 
and the chromatin becomes arranged in irregular clumps through¬ 
out the cytoplasm. The sporulating plasmodia present a cytoplasm 
filled with spherical or oval masses of red chromatin and careful 
examination will demonstrate that each chromatin mass is surround¬ 
ed by a blue-stained ring of the cytoplasm; the pigment is collected 
into one or more irregular masses within the organism along with 
some residual cytoplasm which stains a pale blue. Not infrequently 
free spores, or merozoites , are observed in stained preparations, and 
are composed of a ring-shaped or almost solid mass of blue-stained 
cytoplasm containing a small bright red dot of chromatin. 

Morphology of Plasmodium malarias (the quartan plasmodium ) 
(Schizogony or Human Cycle'). —This species of malaria plasmo¬ 
dium completes its development in man in 72 hours, producing that 
type of the disease characterized by a chill and a rise in temperature 
at the end of every third clay. With the exception of the quotidian 
form of estivo-autumnal infection, this is the most uncommon form 
of malaria. 

Like the tertian plasmodium, the organism causing quartan ma¬ 
larial infections appears at first, in the living specimen, as a small 
actively ameboid hyaline body within or upon the red blood cor¬ 
puscle. It will be noticed that ameboid motion is less marked than 
in the tertian parasite, and that the youngest forms are smaller than 
the youngest forms of the latter species. The quartan parasite rap¬ 
idly becomes pigmented, the pigment being dark brown in color, 
less motile than the pigment of the tertian plasmodium, and ar¬ 
ranged around the periphery of the organism. The outline of the 
parasite, at every stage of development, is much more distinct than 
is that of the tertian parasite, and the infected red corpuscle, instead 


te i 


Bulletin No. 6, Medical Department, U. S. Army. 


PLATE 1 



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V 




























Bulletin No. 6, Medical Department, U. S. Army. 


PLATE 2. 














































































































Bulletin No. 6, Medical Department, U. S. Army. 


PLATE 3. 








25 


PROPHYLAXIS OF MALARIA. 

• 

of being larger than normal, and paler in color, as in tertian infec¬ 
tions, is normal in size throughout the development of the quartan 
plasmodium, and slightly darker green in color than normal. 

The plasmodium slowly increases in size, and becomes less ameboid. 
The pigment increases in quantity and becomes collected at the ex¬ 
treme periphery of the organism, and is immotile. The granules of 
pigment are considerably larger than in the tertian parasite, darker 
in color, and at no stage of the growth of the organism do they col¬ 
lect in small groups throughout the cytoplasm, as is common in the 
tertian organism. As growth increases the plasmodium tends more 
and more to fill the infected red cell, and when full grown—i. e., 
at the end of 72 hours—it almost fills the cell, a narrow greenish rim 
of hemoglobin being all that is visible of the red corpuscle. At this 
stage of its growth the parasite is very distinctly outlined and is 
much more refractive than is the tertian species; the pigment is mo¬ 
tionless and collected around the periphery; the shape is spherical, 
and ameboid motion has entirely disappeared. At the end of 72 
hours sporulation occurs, the pigment being collected in the center, 
or in a star-like arrangement distributed from the center. Radial 
striations appear, dividing the organism into 8 to 12, sometimes 
16, segments or spores. The spores, or merozoites , are generally 
arranged in a perfectly symmetrical manner around the central 
clump of pigment, giving the so-called daisy or “ Margurite ” ap¬ 
pearance to the parasite at this stage of development. When sporu¬ 
lation is complete, each merozoite becomes free in the blood plasma 
and, in the human cycle, again invades a red blood corpuscle and 
repeats the process of development briefly described. 

In stained preparations, if Wright’s method be employed, the 
quartan plasmodium stains in the same general manner as does the 
tertian, the chromatin of the nucleus staining a ruby red, and the 
cytoplasm a robin’s egg blue. The youngest schizonts are the so- 
called a ring-forms ” consisting of a ring of blue-stained cytoplasm, 
with a dot or two of red chromatin somewhere near the periphery; 
while the older forms present the same general staining character¬ 
istics of the tertian plasmodium, although the cytoplasm stains more 
intensely blue and the organism is smaller at every stage of devel¬ 
opment. 

In stained preparations made during the second day of devel¬ 
opment the very characteristic u band forms ” of Plasmodium mala¬ 
rias may be observed consisting of a band of blue-stained cytoplasm 
stretching across the infected red corpuscle and inclosing a mass of 
rubv red chromatin. I have never observed these “ band forms ” 
in any other variety of malarial infection, and a diagnosis of quartan 
malarial fever is justified when such forms are observed. 


26 


PROPHYLAXIS OF MALARIA. 


The merozoites or spores consist of a deep blue stained mass of 
cytoplasm containing a compact clump of dark red chromatin situ¬ 
ated somewhere near the periphery. In most instances the mass of 
chromatin is surrounded by a clear, unstained halo representing the 
unstained portion of the nucleus. 

Morphology of Plasmodium falciparum. Tertian estivo-outumnal 
plasmodium (Schizogony or Human Cycle'). —As I have stated, I 
believe that there are two distinct varieties of the estivo-autumnal 
plasmodium, the tertian and quotidian. These are distinguishable 
microscopically, and the symptoms produced by them are character¬ 
istic and easily differentiated clinically. The most common species 
is the tertian or Plasmodium falciparum , and this will first be de¬ 
scribed. 

EXPLANATION OF PLATE 4. 

Figure 1.— Plasmodium malaria. (Quartan plasmodium.) Young parasites. 

The so-called ring forms. Wright’s stain. X 1500. 

Figure 2.— Plasmodium malaria. Half-grown parasite. The so-called band 
form. Wright’s stain. X 1S00. 

Figure 3. — Plasmodium malaria. Three quarters-grown parasite. Wright’s 
stain. X 1500. 

Figure 4.— Plasmodium malaria'. Large band form. Wright’s stain. X 1800. 

EXPLANATION OF PLATE 5. 

Figure 1.— Plasmodium malaria. (Quartan plasmodium.) Pre-sporulating 
parasite. Wright’s stain. X 1500. 

Figure 2.— Plasmodium malaria. Sporulating parasite. Wright’s stain. X 1200. 
Figure 3. — Plasmodium malaria. Sporulating parasite. X 1200. 

Figure 4.— Plasmodium malaria. Young gamete. X 1800. 

Plasmodium falciparum appears first within or upon the infected 
red corpuscle as a round hyaline ring or disk. The infected cell is 
greenish in color, smaller than the normal corpuscles surrounding 
it, and generally crenated. These young “ring-forms" are irregular 
in outline, one portion of the ring being larger than the rest, giving 
it the so-called “signet-ring" appearance. The organism is quite 
actively ameboid and only rarely is there more than two parasites 
observed within one corpuscle. In the course of from 20 to 24 
hours the hyaline forms become pigmented, the pigment occurring 
in the form of fine, reddish-brown granules somewhat resembling 
those found in the tertian parasite. The pigment is in larger amount 
than in the quotidian plasmodium and is generally motile. As soon 
as pigmentation occurs the parasites collect in the internal organs, 
and it is therefore rare to find the half and fully grown forms of 
this plasmodium in the peripheral blood. 

As growth increases ameboid motion becomes lost and at the time 
of segmentation or sporulation, which occurs at the end of 48 hours 


Bulletin No. 6, Medical Department, U. S. Army 


PLATE 4 
















































' 











■ 

































Bulletin No. 6, Medical Department, U. S. Army. 


PLATE 5, 



4 




■Vi 










;T 

i 

i 
















PROPHYLAXIS OP MALARIA. 


27 


in this species, ameboid motility is entirely absent. At this time 
the fully developed parasite fills slightly more than half of the in¬ 
fected cell, the pigment is collected at the center in a small compact 
almost black mass, and radial striations are noted dividing the para¬ 
site into from 10 to 15 segments or merozoites. In some instances 
as high as 21 merozoites have been observed. Sporulation occurs 
within the red blood corpuscle and considerable of the infected cell 
is still undestroyed at the time that sporulation begins. The spor- 
ulating forms occur very rarely in the peripheral blood, but are 
present in large numbers in the capillaries of the internal organs, 
notably the spleen, liver, and brain, and in the bone marrow. 

In stained preparations, using the Wright method, the staining 
reactions are the same as occur in Plasmodium vivax and Plasmo¬ 
dium malaria >, the differential diagnosis resting upon certain mor¬ 
phological features to be noted later in this contribution. 

Morphology of Plasmodium falciparum quotidianum. Quotidian 
esttco-autumnal plasmodium (Schizogony or Human Cycle). —The 
quotidian estivo-autumnal plasmodium, in the living condition, is 
noticed fust within or upon the red blood corpuscle as a very minute 
ring-shaped or disk-like hyaline body, which upon close inspection is 
seen to have a very active ameboid motion, the periphery of the 
parasite continually changing in appearance, due to the protrusion 
and retraction of minute pseudopodia. The outline of the organism 
at first is indistinct, but becomes more distinct as growth proceeds, 
and when the parasite is fully developed the outline is very clear cut 
and the organism is very refractive. The infected red corpuscle is 
generally smaller in size than the normal corpuscle, darker green or 
“ brassy ” in color, and frequently crenated, and in many instances 
triple infection of the corpuscle is observed. In the peripheral blood 
the hyaline, round or “ ring-shaped ” organisms are those which 
are most frequently observed, although a small number of the 
younger pigmented forms are not uncommon. The pigment consists 
of a small, solid block or mass, almost black in color, situated at 
some portion of the periphery of the parasite, or at the center, and 
is never motile. Very rarely the pigment consists of fine granules, 
but the granules never number more than three or four. 

In this species of plasmodium sporulation occurs at the end of 24 
hours, and the sporulating forms are very rarely observed in the 
peripheral blood, although blood from the spleen taken at the proper 
time will present numerous segmenting organisms. Just before 
sporulation the plasmodium occupies a little more than one-fourth 
of the infected corpuscle, thus easily distinguishing it from Plas¬ 
modium vivax or Plasmodium malaria which entirely fill the red 
blood cell when fully developed. As sporulation begins the pigment 


28 


PROPHYLAXIS OP MALARIA. 


collects in a small perfectly spherical mass at the center of the para¬ 
site, and radial striations may be detected dividing it into from 16 
to 18 very minute round or oval segments, or merozoites. While in 
infections with the tertian and quartan plasmodia it is often almost 
impossible to distinguish the remains of the red corpuscle when 
sporulation occurs, in this species it can be plainly seen that sporu- 
lation occurs before the corpuscle is entirely destroyed, as the sporu- 
lating organism occupies less than half of the cytoplasm of the red 
cell. 

In stained specimens this species presents the same staining reac¬ 
tions as the other malaria plasmodia, but differentiation is compara¬ 
tively easy owing to the minute size of this organism. 

The morphology of the various malaria parasites so far described 
is that peculiar to the forms that develop alone in man , but in every 
variety of malarial infection certain forms of the plasmodia are 
noted that are intended to complete their life cycle within the mos¬ 
quito, and which, so far as definite evidence now goes, never com- 

EXPLANATION OF PLATE 6. 

Figure 1.— Plasmodium falciparum. (Estivo-autumnal plasmodium.) Yovmg 
parasites. The so-called “ ring forms.” Wright’s stain. X 1200. 
Figure 2 .—Plasmodium falciparum. Speculating parasite and several young 
“ ring forms.” Wright’s stain. X 1800. 

Figure 3 .—Plasmodium falciparum. Speculating parasite. Wright’s stain. 
X 1800. 

Figure 4 .—Plasmodium falciparum. Free spores or merozoites. Wright’s stain. 
X 1500. 

plete a life cycle within man. These forms are known as gametes 
and probably develop from sporozoites in answer to certain influences 
produced upon the schizonts by life within man. While certain 
authorities believe that the gametes are introduced as such by the 
mosquitoes or develop from certain differentiated sporozoites , the 
great mass of evidence is in favor of their development within man 
from certain schizonts , for it is well known that they do not appear 
until an infection has lasted for several days, and never appear if the 
infection is properly treated. These forms will now be described, 
but before doing so it will be necessary to briefly sketch the life cycle 
of the malarial plasmodia within the mosquito in order to under¬ 
stand the names applied to the various stages during this cycle of 
development. 

Development of the malaria plasmodia within the mosquito 
(Sporogony or mosquito cycle). —In tertian and quartan infections 
certain of the plasmodia are observed that do not sporulate, but 
remain unchanged in the blood of man until they are removed, when 
changes occur that normally should occur in the stomach of the 


Bulletin No. 6, Medical Department, U. S. Army. 


PLATE 6 








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Bulletin No. 6, Medical Department, U. S. Army. 


PLATE 7. 














PROPHYLAXIS OF MALARIA. 


29 


mosquito. These bodies are circular in shape when fully developed 
and can be differentiated in both the living condition and in stained 
preparations. Likewise, in the estivo-autumnal infections certain 
bodies are developed, of typical crescentic shape, the so-called “ cres¬ 
cents," that only undergo development within the mosquito. These 
bodies while in the blood of man are known as gametes and are 
sexually differentiated, the male being known as the microgame- 
tocyte and the female as the macrogametocyte. When they reach 
the stomach of the mosquito the male, or microgametocyte, liberates 
liagella, which are known as microgametes, and which serve to fer¬ 
tilize the female macro gametocyte , which, after certain maturation 
phenomena, is now known as the macrogamete. This process may 
rarely be observed in preparations of blood removed some time from 
the body if a little moisture be present on the slide and the tempera¬ 
ture be suitable. The fertilization of the macrogamete occurs nor¬ 
mally in the middle intestine of the mosquito and the result of the 
fertilization is known as the sporont. After a certain period of 
time the sporont elongates and becomes motile and is then known as 
the ookinete. The ookinete penetrates the wall of the middle intestine 
of the mosquito and eventually becomes situated between the adi¬ 
pose tissue and the muscular wall of the intestine. Here the organ¬ 
ism becomes circular in shape and forms a cyst known as the oocyst. 
At this stage the cytoplasm is reticular and granular in appearance, 
the pigment is reduced in amount, and the entire organism is inclosed 
in a well-defined capsule. The oocyst is formed at about the third or 
fourth day after infection of the mosquito. About the fifth or sixth 
day the oocyst enlarges and within it are formed spherical refractive 
bodies known as sporoblasts. At this stage the organism is so greatly 
increased in size that it projects from the intestinal wall and may be 
seen with a low-power objective. At the end of a week the sporo¬ 
blasts have produced a large number of delicate filaments having 
pointed extremities and containing a small amount of chromatin, 
which are called sporozoites. They are about 14 microns in length and 
are arranged in a ray-like formation about a central mass in the 
sporoblast , which may contain pigment. The sporozoites are finally 
liberated in the body-cavity of the mosquito by the rupture of the cyst 
and make their way to the tubules of the salivary glands. At this 
time, if the infected mosquito bites a man, the sporozoites will be 
inoculated, taken up by the blood stream, and penetrating the red 
blood corpuscles, develop into schizonts and thus begin the human 
life cycle of plasmodia. The entire life cycle in the mosquito varies 
from 10 to 14 days in duration. 

Having thus briefly reviewed the mosquito-cycle of the malaria 
plasmodia, we will now consider the morphology of those fonns 


30 


PROPHYLAXIS OF MALARIA. 


which occur in the blood of man and which are intended to complete 
their development in the mosquito. 

Morphology of the sexual forms of the plasmodia occurring in 
the blood of man .—The forms of the malaria plasmodia concerned 
in sporogony , or the mosquito cycle of development, which can be 
demonstrated in the blood of the human host are of the greatest 
importance in the prophylaxis of these infections, and their recog¬ 
nition essential in any scientific campaign against malaria. The 



Fig. 1. — Development of Plasmodium vivax within the mosquito. 1, Ookinete; 2, oocyst : 
3, 4, 5, oocysts showing the development of sporoblasts; 6 and 7, oocyst showing 
development of the sporozoites, which are fully formed in 7 ; 8, sporozoites within a 
cell of the salivary gland ; 9, sporozoites ; 10, entrance of sporozoite into a red blood 
corpuscle; 11, middle intestine (stomach) of mosquito, showing several oocysts in the 
wall of the organ. (Original.) 


presence of these sexual forms proves beyond question that the indi¬ 
viduals in whom they occur are infective to mosquitoes, and that they 
are thus true u carriers “ of malarial disease. The proper treatment 
of these “ carriers *' is thus dependent upon the differentiation of the 
sexual forms or gametes and no malaria survey can be considered 
complete unless the percentage of individuals showing gametes is 
ascertained and proper measures be taken to render them harmless. 
As already stated, the gametes are sexually differentiated, the male 
being called a microgametocyte and the female a macrogametocyte, 





PROPHYLAXIS OF MALARIA. 


31 


but for convenience of description I shall refer to them as the male 
and female gamete respectively. 

While no true development of the gametes occurs within man, 
if blood containing them be removed from the body, the male gamete 
frequently undergoes flagellation and liberates the micro gametes, a 
process normallv occurring in the middle intestine of the mosquito. 
In very rare instances the fertilization of the female gamete by one 
of these microgametes may be observed in the blood after removal 
from the body, but this can only be regarded as an accidental occur¬ 
rence, as it normally occurs only within the infected mosquito. The 
differentiation of the sexual forms or gametes is not a very diffi¬ 
cult matter, although the opposite opinion appears to be generally 
prevalent. The estivo-autumnal gametes , because of their crescentic 
shape when fully developed, are easily recognized, even bv a novice 
in malarial parasitology, but the intracorpuscular stages in the de¬ 
velopment of the gametes of all of the species of plasmodia are more 
difficult of recognition, although with a clear knowledge of their 
morphology and a little practice all of the stages of development 
may be differentiated in stained preparations of blood. The fully 
developed gametes of Plasmodium vivax (the tertian plasmodium) 
and of Plasmodium malarias (the quartan plasmodium) are easily 
differentiated if one is acquainted with their morphology. 

In considering the morphology of the gametes it will be necessary 
to describe that of each species, as observed in both fresh and stained 
specimens of blood. The description given will include only the 
salient diagnostic points, and will be found true of the vast majority 
of organisms, although frequent deviations will be observed due to 
artefacts produced during the staining process or to developmental 
anomalies brought about by adverse conditions in the human host. 
(The stain used was Wright’s modification of the Romanowsky 
method, already described.) 

The gametes of Plasmodium vivax (the tertian plasmodium). 
Fresh preparations. —In fresh preparations it is practically impos¬ 
sible to distinguish the gametes of Plasmodium vivax from the 
forms of the human life cycle until they are fully developed. While 
individual gametes may contain a larger amount of pigment, which 
is coarser in structure, this distinction can not always be made. How¬ 
ever, when the gametes are fully developed they may be easily dis¬ 
tinguished, even when unstained, from the fully developed forms of 
the human cvcle, and the male and female forms can be readily dif- 
ferentiated. 

The male Gamete or Microgametocyte. —The living microgamet- 
ocyte of Plasmodium vivax , when fully developed, measures from 
8 to 10 microns in diameter, and almost fills the infected red cor¬ 
puscle; it is spherical in shape and is more or less filled with dark 


32 


PROPHYLAXIS OF MALARIA. 


brown pigment collected in small clumps throughout the cytoplasm. 
The pigment may be very motile, especially just before exflagellation, 
and this serves to distinguish it from the female gamete , in which 
the pigment is motionless. 

The phenomenon which distinguishes the living microgametocyte 
from the forms occurring in the human life cycle is the process 
known as flagellation, during which the microgametes are finally 
extruded and liberated from the parent organism. The gametes 
that are about to undergo this change are easily recognized because 
of the violent activity of the pigment within them, and the undu- 
latorv movements of the periphery of the parasite, due to the flagella 
or microgametes moving about within the organism. If such a para¬ 
site be watched it will be observed that eventually a number of deli¬ 
cate filaments suddenly make their appearance at the periphery of 
the organism and lash about in the blood plasma. After a variable 
time one, or perhaps all, of the flagella or microgametes succeed in 
freeing themselves from the parent body and disappear among the 
red-blood corpuscles. Sometimes these free microgametes are dis¬ 
covered apparently alone in a blood specimen by the movement 
which they impart to the red corpuscles in their vicinity and have 
been mistaken for very minute filarioe. Their presence is sufficient 
to stamp the individual from whom the blood was obtained as a 
u carrier ” of malaria. 

The female gamete or macrogametocyte. —The tertian macrogame- 
tocyte when fully developed measures from 9 to 11 microns in 
diameter, is circular in shape, and almost fills the infected red cell. 
The cytoplasm is more granular than is that of the forms of the 
human life cycle, and the pigment is coarser in character and instead 
of being distributed throughout the cytoplasm is collected in a 
wreathlike manner at some distance from the periphery. The pig¬ 
ment is not motile. The arrangement of the pigment is characteristic 
and is of great value in the diagnosis of this gamete in living 
specimens. 

Stained preparations. —While it requires considerable practice to 
distinguish the gametes of the tertian plasmodium from the forms 
concerned in the human life cycle in living specimens, it is quite 
easy to make the distinction in stained preparations, and in such 
preparations even the young gametes may be differentiated from the 
“ ring-forms ” of the human cycle. The staining reactions of the 
cytoplasm and nucleus of the malaria plasmodia have already been 
described, and the only variation that occurs in the staining reactions 
of the gametes consists in the degree of color imparted by the stain 
to the various forms. The tertian gametes when stained with the 
Wright method consist of a mass of blue cytoplasm, inclosing the 


PROPHYLAXIS OF MALARIA. 


33 


red-stained chromatin; the unstained portion of the nucleus is not 
always distinct, and the gamete is considerably larger in every stage 
of development than the schizont. The pigment is more abundant, 
while the nuclear chromatin shows no evidence of division and dis¬ 
tribution throughout the cytoplasm, being arranged in small irregu¬ 
lar masses confined to one portion of the parasite, or in fine threads 
or grains, surrounded by an unstained area, which in turn is sur¬ 
rounded by the blue cytoplasm. 

The following points are of service in differentiating tertian 
gametes from the schizonts , or forms concerned in the human life 
cycle: 1. The young gamete is never “ ringlike ” in shape, as the dot 
of nuclear chromatin is situated within the circular parasite instead 
of at some portion of the periphery. This “ bull’s-eye ” arrangement 
is characteristic, and any organism presenting it may be diagnosed 
as a gamete. 2. The gamete is larger than the corresponding stage 
in the development of the schizont. 3. The pigment in the gamete 
is larger in amount and earlier developed. 4. The chromatin is not 
distributed in the cytoplasm, but occurs in a clump surrounded by 
the cytoplasm. 5. Gametes never sporulate. 

The male gamete or microgametocyte varies in appearance when 
stained with the stage of development. The small, intracorpuscular 
gametes stain a pale blue and contain a large dot of intensely red 
chromatin situated centrally. The fully developed microgameto- 
cytes present a very poorly stained cytoplasm, the blue tinge being 
so faint in many instances as to be distinguished with difficulty, the 
cytoplasm appearing hyaline. The chromatin is large in amount, 
and in those organisms about to flagellate it is collected into several 
masses, which are arranged about the periphery of the organism. 
The pigment is large in amount and stains a greenish-blue color. 

The chromatin in the microgametocytes is always larger in amount 
than in the female gamete or macrogametocyte, and is arranged in 
the form of rather thick fibrils collected in irregular masses in the 
cytoplasm, but all of them surrounded by a single achromatic zone, 
except just prior to exflagellation. 

The female gamete or macrogametocyte of the tertian plasmodium 
stains a very intense blue, and this alone serves to distinguish it from 
the male gamete or the schizont , neither of which stain so intensely. 
The chromatin in the smallest forms appears as a single red dot 
situated near the center of the organism, while in later stages of 
development several dots or rods of this substance are present, situ¬ 
ated near the periphery and surrounded by an achromatic zone. The 
chromatin is never distributed in the cytoplasm as in the schizonts 
or in the male gamete just prior to flagellation. The pigment is 

58000°—14 


3 



34 


PROPHYLAXIS OF MALARIA. 


almost black in color, occurs in the form of minute rods, and is 
arranged in irregular masses near the periphery or in a wreath about 
the center of the organism. 

The tertian microgametocyte may be distinguished from the mac- 
rogametocyte , in stained specimens, by the pale blue staining of the 
cytoplasm as compared with the deep blue of the macrogametocyte , 
the larger amount of chromatin, collected in masses and surrounded 
by an achromatic zone, and the presence of several irregular masses 
of chromatin, situated near the periphery, when the organism is 
about the flagellate. In the young gametes it is impossible to dis¬ 
tinguish between the male and female forms, except by the stain¬ 
ing reaction of the cytoplasm, the male staining a very pale blue, 
while the female stains a deep blue. 

The gametes of Plasmodium malaria (the Quartan Plasmo¬ 
dium).—The gametes of Plasmodium malaria are very similar to 
those of Plasmodium vivax , which have just been described, and 
for this reason require no extended description. Allowing for the 
difference in the size of the two species, the staining reactions, and 
the differentiation of the male and the female forms are practically 
identical, and the description of one can be used for the other if it 
be remembered that the quartan gametes , at every stage of develop¬ 
ment, are much smaller than the tertian. 

The gametes of the estivo-autumnal plasmodia .—The sexual 
forms, or gametes , of Plasmodium falciparum and Plasmodium fal¬ 
ciparum quotidianum are commonly known as “ crescents,” and are 
easily distinguished from any other form of plasmodium. The 
presence of these crescents in the blood at once stamps the individual 
as a “ carrier ” of malaria, but the early stages of the estivo-autum- 
nal gametes are not crescentic in shape, and at this time it is im¬ 
possible to differentiate them from the quartan gametes , as they 
are similar in structure and in size. When fully developed the cres¬ 
cents are easilv recognized, and the male and female forms can be 
differentiated with little trouble. 

What has been said regarding the appearance of gametes of ter¬ 
tian malaria in the earlier stages of development is equally true of 
the gametes of the estivo-autumnal plasmodia, and it is only after 
they have assumed the crescentic shape that they can be said to 
differ in morphology from the tertian or quartan gametes , if we 
except their size, which is slightly smaller than the quartan and 
much smaller than the tertian gamete. It will not be necessary, 
then, to describe the early stages of development of these bodies, but 
only their morphology after the typical crescentic shape has been 
acquired. This occurs while the parasites are still within the in¬ 
fected red. corpuscle, and as the organism gradually enlarges the 
infected cell shrinks about it, forming an envelope, which is most 


PROPHYLAXIS OF MALARIA. 


35 


noticeable between the poles of the crescent, where it forms what is 
known as the “ bib ” of the crescent. 

As the gametes of the tertian and quotidian estivo-autumnal 
plasmodia are identical in morphology, except that the quotidian 
gametes are considerably smaller than the tertian, they will not be 
described separately, and only the points of diagnostic importance 
will be touched upon in the description of these stages of devel¬ 
opment. 

In the living condition the estivo-autumnal gametes , after reach¬ 
ing the crescentic stage, are distinguished by their typically crescentic 
outline and by the fact that they appear to be extracellular, in the 
vast majority of instances. The cytoplasm appears granular in 
structure, the female form being more granular than the male, and 
the pigment is dark brown in color and either distributed throughout 
the cytoplasm or collected near or at the center of the crescent. The 

EXPLANATION OF PLATE 7. 

PLATE 7. 

Figure 1. —Phagocytosis of spomlating Plasmodium falciparum. Wright’s stain. 
X 1800. 

Figure 2 .—Plasmodium falciparum. A macrogametocyte. The female crescent 
or gamete. Wright’s stain. X 1200. 

Figure 3. —Plasmodium falciparum. A macrogametocyte. The female gamete 
or crescent. Wright’s stain. X 1500. 

Figure 4. — Plasmodium falciparum. A microgamctocytc. The male gamete or 
crescent. Wright’s stain. X 1200. 

male crescent, or gamete , is easily distinguished from the female by 
its plump kidney-like shape, the female crescent being long and 
slender. These bodies are very easily recognized in unstained speci¬ 
mens of blood and in regions where estivo-autumnal malaria is 
endemic a considerable proportion of the inhabitants will be found 
to show them in their blood. 

In stained preparations the crescents present the same staining 
reactions as do the gametes of the tertian and quartan parasites, the 
male crescent staining a pale blue while the female stains intensely. 
The following features serve to distinguish the estivo-autumnal 
microgametocytes (males) from the macrogametocytes (females) : 

1. Shape: The plump kidney shape, the macrogametocyte being 
long and slender. 

2. Staining reaction: The pale blue staining of the cytoplasm, the 
macrogametocyte staining deep blue. 

3. Chromatin: The arrangement of the nuclear chromatin in the 
form of a loose network, the chromatin of the macrogametocyte being- 
situated at the center of the crescent in a dense mass, 


36 


PROPHYLAXIS OF MALARIA. 


4. Pigment: The distribution of the pigment throughout the cyto¬ 
plasm, the pigment of the macrogametocyte being concentrated at or 
near the center. 

5. Size: The microg ametocyte s are shorter and broader than the 
macrog ametocytes. 

I do not consider it necessary to describe more minutely the mor- 

«/ */ 

phology of the estivo-autumnal gametes , as their crescentic shape is 
sufficient to distinguish them in either fresh or stained preparations 
of blood, and as their recognition is only of importance in malaria 
prophylaxis, this end will be attained bv attention to the diagnostic 
points already mentioned. For a more detailed description the reader 
is referred to any of the modern works dealing with the malarial 
fevers. 

It should be remembered that after the crescents reach the middle 
intestine of the mosquito the crescentic shape is lost; they become 
circular in outline, the male crescent flagellates, and the flagella, or 
microgametes , are liberated and fertilize the female, as in the tertian 
and quartan parasites, after which a similar cycle of development 
occurs in the mosquito. The process of flagellation is often observed 
in blood removed some time from the body, especially if a little 
moisture is present upon the microscopic slide. 

Important differential points in the diagnosis of the species of 
malaria plasmodia. —The various species of malaria plasmodia may 
be easily differentiated in both fresh blood and in stained prepara¬ 
tions if certain morphological peculiarities of the plasmodia and the 
cells infected by them be remembered. The following points I have 
found most useful in differentiating the various species: 

A. Plasmodium vivax (tertian plasmodium). 

Unstained preparations. —1. Comparatively large size of parasite 
after development of pigment. 2. Enlargement of the infected red 
blood corpuscle. 3. Active ameboid motility. 4. Fine, light-brown 
or reddish-brown pigment. 5. Number of spores or merozoites , 12 
to 24. 6. All stages of development present in the peripheral blood. 

Stained preparations. —1. Large size, after development of pig¬ 
ment. 2. Increased size of the infected erythrocyte. 3. Presence of 
Schuffner's dots (eosinophilic granules) in cytoplasm of infected 
erythrocyte. 4. Number of merozoites. 12 to 24. 5. Presence of all 
stages in the peripheral blood. 

B. Plasmodium malarice (quartan plasmodium). 

Unstained preparations. —1. Medium size, after development of 
pigment. 2. Pigment in coarse, dark-brown granules, arranged about 
periphery of organism. 3. Infected erythrocyte not enlarged at any 
stage of development. 4. Presence of all stages in peripheral blood. 
5. Number of merozoites , 6 to 12, 


PROPHYLAXIS OF MALARIA. 


37 


Stained preparations. — 1 . Medium size of pigmented organisms. 
2. No increase in the size of the infected red blood corpuscle. 3. Ab¬ 
sence of Schuffner’s dots (eosinophilic granules) in cytoplasm of 
infected cell. 4. Number of spores {merozoites) , 6 to 12. 5. Pres¬ 
ence of all stages in the peripheral blood. 6. Presence of the “band 
forms.” 

C. Plasmodium falciparum (tertian estivo-autumnal plasmodium). 

Unstained preparations. —1. Small size, even when fully devel¬ 
oped. 2. No enlargement of infected corpuscle, which is smaller 
than normal. 3. Small amount of fine brownish pigment. 4. Num¬ 
ber of merozoites . 10 to 10. 5. Only ring forms and young pigmented 
forms present in the peripheral blood, and crescents. 0. Crescentic 
shape of the gametes. 

Stained preparations. — 1. Small size, even the sporulating forms 
only partly filling the infected cell. 2. No enlargement of the in¬ 
fected corpuscle. 3. Presence of Maurer’s dots or basophilic gran¬ 
ules in the cytoplasm of the infected cell. 4. Number of merozoites , 
10 to 16, as a rule, very small and arranged irregularly. 5. Only 
“ ring-forms ” and young pigmented forms occur in the peripheral 
blood, as a rule, together with crescents after the infection has 
persisted for several days. (>. Crescentic shape of the gametes. 

D. Plasmodium falciparum quotidianum (quotidian estivo-autum¬ 
nal plasmodium).—The quotidian estivo-autumnal plasmodium dif¬ 
fers from the tertian form, in both fresh and stained preparations, 
by its smaller size at every stage of development, while the mero¬ 
zoites number from 6 to 18, the average being from 12 to 14. The 
organism contains less pigment, which is collected into one or two 
almost black masses, and the sporulating forms seldom fill more than 
one-third of the infected red blood corpuscles. The hyaline “ ring- 
forms ” are very minute, resembling in this respect the piroplasma. 

Objects which mag be mistaken for plasmodia in stained, and un¬ 
stained specimens of blood. —There is no one thing more essential to 
success in the recognition of the malaria plasmodia than a practical 
knowledge of the miscroscopical appearance of both fresh and stained 
specimens of normal and pathological blood. It is surprising how 
often some artefact or other object is mistaken for a malaria plas- 
modium by medical men from whom such a mistake would not be 
expected, and it is always due to ignorance of the morphology of 
the blood, an ignorance that can not be excused, for the blood “we 
have always with us" and anyone may be become perfectly familiar 
with its morphology who capes to take the time to make a few prep¬ 
arations and to study them. Mistakes are more apt to occur in ex¬ 
amining fresh blood but a little care and practice will enable one 
to avoid them and with the excellent Wright stain it is inexcusable 
to mistake any object for a plasmodium in stained preparations. 


38 


PROPHYLAXIS OF MALARIA. 


In fresh specimens of blood the following may be mistaken for 
malaria plasmodia: 

Vacuoles. —There is no object more deceiving in fresh blood pre¬ 
parations than a small vacuole within the red corpuscle, especially 
if the border of the vacuole alter in shape, when the resemblance to 
the hyalin disk forms of the various plasmodia is really very strik¬ 
ing. The greater refraction of the vacuole and the fact that it grows 
larger and smaller in focussing up and down upon it should dis¬ 
tinguish it from any stage in the growth of the malaria plasmodia. 

Retraction of the hemoglobin from the edge of the red corpuscle 
mav sometimes cause the area devoid of hemoglobin to resemble a 
hyalin plasmodium, but it may be distinguished by the lack of ame¬ 
boid motion and the sharp edge of the hemoglobin layer. 

“ Eye-spots ,” or areas devoid of hemoglobin, occurring within the 
red corpuscles are sometimes observed in normal blood, and fre¬ 
quently in typhoid fever, tuberculosis, pneumonia, and other acute 
infectious diseases. They are apparently due to retraction of the 
hemoglobin layer of the corpuscle, and may be round, oval, spindle- 
shaped, or ring-shaped, and situated at any portion of the corpuscle. 
Many of them are oval and spindle-shaped and contain a dark area 
at the center resembling pigment. These “ eye-spots" have been 
very often mistaken for malaria plasmodia and have been described 
by several observers as new blood parasites of man. The absence of 
distinct ameboid motion and the greater degree of refraction should 
serve to distinguish them from malaria plasmodia. 

Blood platelets. —A blood platelet, if lying upon a red corpuscle, 
resembles slightly the hyalin disk form of malaria plasmodia, but 
upon focussing there will be observed a difference in the level of 
the two bodies, while the platelet has no ameboid motility and is 
less opaque than the plasmodia. 

Granules derived from broken down leucocytes, which possess 
active Brownian movements, may be confused with the smallest 
forms of plasmodia if they become attached to, or lie over, the red 
blood corpuscles. Their smaller size and different structure should 
render such a mistake impossible. 

The normal lighter colored center of the red corpuscle, which is 
often hyalin in appearance in diseases accompanied by anemia, has 
often been confused with the hyalin malaria plasmodia, and I have 
several times been shown cells of this character and told that they 
contained plasmodia. Such a mistake is due to inexcusable igno¬ 
rance of the morphology of the red blood corpuscle. 

Cremations of the red corpuscle may cause some trouble to the 
beginner if they be looked down upon directly, as they then appear 
as round, hyalin bodies lying upon the red cell, and are sometimes 
slightly motile. However, there is no ringlike outline, and when 


PROPHYLAXIS OF MALARIA. 39 

focussed upon they appear as alternately light and dark areas upon 
the surface of the red corpuscle. 

Among other bodies that have been mistaken, in my experience, 
for malaria plasmodia, and shown to me, may be mentioned yeast 
cells, bacteria of various kinds, extraneous matter, and degenerating 
red blood corpuscles possessing slender cytoplasmic processes. The 
latter have been mistaken for flagellating plasmodia, but the greenish 
color and lack of pigment should prevent such a mistake. 

In specimens of blood stained by Wright's method the following 
have been mistaken for malarial plasmodia: 

Blood plates .—There is no object so frequently mistaken for mala¬ 
ria plasmodia in stained preparations of blood as is the blood 
platelet, especially when it lies upon a corpuscle, but such an 
error is impossible if one is familiar with the morphology of the 
platelet. The malaria plasmodia of a similar size may always be 
differentiated from the platelets by their blue-stained cytoplasm and 
the solid, compact mass or masses of chromatin which stain a ruby 
red color. The chromatin of the blood platelet stains a darker 
color and is distributed throughout the platelet in the form of fine 
granules or irregular granular masses. If one remembers that any 
malaria plasmodium the size of a blood platelet consists only of a 
mass of blue-stained cytoplasm containing a solid spherical dot, or 
at most two dots, of chromatin, it will be impossible to confuse it 
with a blood platelet, which has a practically unstained cytoplasm 
and in which the chromatin is granular and collected in a mass or 
masses in the cytoplasm. Not frequently blood platelets may be 
collected in crescentic shaped clumps and these have been mistaken 
for crescents, but no one in the least familiar with the plasmodia 
could make such a mistake. 

Flaws in the microscopic slide, in which some of the stain has 
settled, have caused confusion, especially if overlaid by a red-blood 
corpuscle, but focussing will show that they are on a different level 
from the corpuscle, and a study of the staining reaction will imme¬ 
diately demonstrate their nature. 

Vacuoles in the red cell, which sometimes retain a little of the 
stain, may slightly resemble some of the stages of development of 
the plasmodia, but may be easily distinguished from the plasmodia 
by the absence of the blue-stained cytoplasm and red chromatin 
always present at every stage in the development of the malaria 
parasites. 

Among other objects which have been confused with the plasmodia 
in stained smears may be mentioned degenerating erythrocytes and 
leucocytes, yeast cells, and other microorganisms, nucleated erythro¬ 
cytes, basophilia of the erythrocyte, and extraneous bodies of various 
nature. It is perfectly obvious that a knowledge of the appearance 


40 


PROPHYLAXIS OF MALARIA. 


of normal and pathological blood in stained preparations will make 
such mistakes impossible, and this is absolutely essential to one who 
expects to make microscopic examinations of the blood for the 
diagnosis, and as an aid in the prophylaxis, of malarial infections. 
In the military service our entire system of prophylaxis and treat¬ 
ment of malaria should be based upon the recognition of the malaria 
plasmodia in man and the mosquito, for in this service the material 
is under absolute control and such a basis for prophylaxis and treat¬ 
ment is possible. 


Chapter IT. 


THE MALARIA MOSQUITOES. 

The Culicidae, or mosquitoes, belong to the true hies, or Diptera, 
and the only insects of this family of interest to us in thp prophylaxis 
of malaria are some of the species belonging to the subfamily Anoph- 
elinw , for it is only species belonging to this subfamily that transmit 
malaria. In this section only those points of interest or value to the 
student of malaria prophylaxis will be touched upon, no attempt be¬ 
ing made to give a complete account of either the anatomy or life 
history of the mosquitoes, as a whole, or to give descriptions of the 
species concerned in the transmission of the malarial infections. For 
a complete discussion of the subject the reader is referred to works 
of Theobald ', Howard, Dyar, and Knabe (i , and Ludlow 7 . 

(ideographical distribution of the Anophelinw .—-Mosquitoes belong¬ 
ing to the Anophelinai occur wherever malaria does, but it does not 
follow that malaria is always present in localities where the Anophe¬ 
linai are found. In order that malarial infections be present in any 
locality, the right species of Anophelinw must be present, together 
with infected individuals, and unless both factors be present the 
propagation of these fevers is impossible. It may be stated that the 
geographical distribution of the malaria mosquitoes coincides with 
the distribution of malaria, and the amount of malaria in any given 
locality is an index of the number of the Anophelince present. 

This fact is of great importance in the prophylaxis of the disease, 
as the determination of the presence of anophelines and of the exact 
species present enables one to avoid localities inhabited by the mala¬ 
ria mosquitoes or to take the proper precautions against infection. 
Such knowledge is of special value in the military service, as a pre¬ 
liminary “ mosquito survey ” in the selection of localities for camp 
sites or for the sites of military posts will often prove of inestimable 
value, both as regards the health of the troops which occupy them 
and the cost of maintenance. Several instances have occurred in 
which this measure was neglected, with the result that the camps or 
posts so located became hotbeds of malaria and a source of continued 
and excessive expense, owing to the necessity of maintaining costly 
prophylactic operations. Where there is no military reason for occu¬ 
pying a malarial locality as a camp site, or as a permanent post, it is 
the part of wisdom to avoid doing so, and the determination of the 

41 


42 


PROPHYLAXIS OF MALARIA. 


species of mosquitoes which may be present and the feasibility of 
getting rid of them should be as carefidly investigated as the char¬ 
acter of the water supply, the terrain, or any other feature of the 
locality. 

The classification of mosquitoes, as regards genera and species, is 
still an unsettled question among entomologists, but in the following 
pages I shall follow that of Theobald, who divides the Anophelince into 
several genera, each containing several species. Of the genera given 
by Theobald, the following contain species that have been proven to 
transmit malaria: Anopheles , Myzomyia , Stethomyia , Pyretophorus, 
Arribalzagia , Myzorhynchus , Nyssorhynchus , and Cellia. 

For convenience of reference I have prepared the following table, 
giving the geographical distribution of the species of mosquitoes 
which have been proven to transmit the malarial fevers. The table 
can not be considered as complete, as observations are being continu¬ 
ally published demonstrating the transmission of these infections by 
hitherto unsuspected species of the Anophelince , but it will serve as 
a guide to the commonly observed species which transmit malaria in 
the regions mentioned. 




Locality. 


Species of malaria mosquitoes. 


United States 


West Indies. 

Canal Zone, Panama. 

Philippine Islands. 

Central and South America.... 

I 

Europe. 

Asia.I 


Africa 


Cellia albimanus, Cellia argyritarsis, Anopheles macvlipennis, Anopheles 
quadrimaculatus, Anopheles crucians, Anopheles intermedium , Anopheles 
pseudomaculipes, Anopheles pseudopunctipennis, Anopheles tarsima- 
culata. 

Cellia albimanus, Cellia argyritarsis. 

Cellia argyritarsis, Cellia albimanus, Anopheles pseudopunctipennis, Ano¬ 
pheles iarsimaculata. 

Myzomyia funesta, Myzorhynchus sinensis, Myzorhynchus barbirostris, 
Myssorhynchus fuliginosus, Myzomyia ludlovciif 

Anopheles albipcs, Pyrctophorus lutzii, Cellia argyritarsis, Cellia albimanus, 
Anopheles pseudomaculipes, Anopheles intermedium, Anopheles cruzii. 

Anopheles maculipennis, Anopheles bifurcatus, Anopheles superpictus, 
Myzomyia hispaniola, Myzorhynchus pseudopictvs. 

Myzomyia culicifacies, Myzomyia listonii, Myzomyia turkhudi, Myzorhyn¬ 
chus barbirostris, Myzorhynchus sinensis, Nyssorhynchus theobaldi, Nys¬ 
sorhynchus stephensii, Nyssorhynchus fuliginosus, Nyssorhynchus maculi- 
palpis, Pyrctophorus jeyporensis. 

Myzomyia funesta . Myzomyia nili. Myzorhynchus barbirostris, Myzorhynchus 
paludis, Cellia pharoensis, Pyrctophorus costalis, Pyretophorus chaudoyci. 


If one desires to follow the classification of Howard, Dyar, and 
Knab, the generic names in the above table should all be replaced by 
the generic name, Anopheles. 

The number of infected mosquitoes in malarial regions. —It is 
obvious that the number of mosquitoes infected in different localities 
will vary with the number of infected individuals present, the sea¬ 
son of the year, certain atmospheric conditions, and the care observed 
by the inhabitants in protecting themselves from the bites of mos¬ 
quitoes. At the present time we have no evidence that the infection 
in the mosquito is hereditary, so that it follows that every infected 
mosquito must have become infected from a human being, and one 
infected individual may infect scores of mosquitoes within a few 
















PROPHYLAXIS OP MALARIA. 


43 


hours. In practice it has been found that even in the worst malarial 
regions a surprisingly small percentage of mosquitoes examined are 
found infected, if one considers the actual number of infected indi¬ 
viduals present and the apparent chance of infection of the mosquito. 

In Italy Celli found only 2.5 per cent of the Anopheles examined 
by himself infected; A. Plehn, in Africa, examined 860 Anopheles 
and found 2.2 per cent infected; La Monaco found about 5 per cent 
infected; and the Sergents, in Algiers, found 1.6 per cent infected. 
At Camp Stotsenburg, in the Philippine Islands, the percentage of 
naturally infected mosquitoes varied greatly, being as high as 35 
per cent during the height of the malarial season and ns low as 1 
per cent at other times. 

The species of mosquito in relation to the transmission of ma¬ 
laria. —It is now a well-established fact that certain of the Anoplie- 
lince do not transmit malaria and can not be infected experimentally. 
The observations of Stephens and Christophers in India showed 
that while 12 of 259 Myzomyia culicifacfes dissected by them shown 
infection with malarial sporozoites , not a single one of 496 Myzomyia 
rossii showed infection, while Hirshberg found that out of 58 Ano¬ 
pheles punctipennis experimentally none developed an infection, 
while of 48 Anopheles maculipennis 8 became infected. In the Canal 
Zone Darling 8 found that, in his experiments, 70.2 per cent of 
Cellia ( Anopheles ) albimctnus became infected; 60 per cent of Ano¬ 
pheles tarsimaculata , and 12.9 per cent of Anopheles pseudopuncti- 
pennis. On the other hand, he found it impossible to infect Anopheles 
malefactor , which, as he says, despite its name, is not a factor in the 
transmission of malaria in the Canal Zone. 

From these observations it is evident that even though anophelines 
may be present in a locality, it does not follow that malaria is present 
or that the disease could spread if it were introduced. In other 
words, the right species of Anopheles must be present in order to 
transmit the infection, and hence it follows that the determination 
of the species present in any locality becomes an important pro¬ 
phylactic measure. 

Not only are some of the Anophelince unable to act as hosts of the 
malaria plasmodia but some species can only act as host for a 
certain species of plasmodium, so that the prevalence of the dif¬ 
ferent types of malaria in any locality depends upon the species 
of mosquito present. Beyer, Pothier, Couret, and Leman 9 have 
shown that while Anopheles quadrimaculatus became infected ex¬ 
perimentally with the tertian and quartan plasmodia it was impos¬ 
sible to infect it with the aestivo-autumnal plasmodium, while, on 
the other hand, Anopheles crucians was shown to be a host to the 
aestivo-autumnal plasmodium but could not be infected with the 
tertian or quartan plasmodia. Kinosliita 10 found that Anopheles 


44 


PROPHYLAXIS OF MALARIA. 


sinensis could be infected with the plasmodia of tertian and quartan 
malaria but not with those of aestivo-autuninal malaria, and that 
the quartan plasmodium only developed in this species of mosquito 
at low temperatures. He also has shown that Anopheles listoni is 
the great transmitter of the aestivo-autumnal plasmodia in Formosa. 
M any observers have proven that the common Anopheles maculi- 
pennis is an efficient host for all of the species of malaria plasmodia. 

The observations noted explain clearly why certain localities suf¬ 
fer more severely than others from certain types of malarial infec- 
tion. Given a locality in which only Anopheles crucians occurred 
and we would have nothing but aestivo-autumnal infections, as this 
mosquito is unable to transmit the tertian or quartan plasmodia, 
but if Anopheles quadrimaculatus were the only anopheles present, 
we might have either tertian or quartan infections but no aestivo- 
autumnal malaria. It is, therefore, evident that a mosquito survey 
is not only of value in determining whether dangerous species of 
Anopheles are present or not, but that it will also aid us in estimat¬ 
ing the probability of the spread of the various types of malarial 
infection. 

General description of the Anophelince. —The following brief de¬ 
scription of the anatomy of the Anophelince only includes the points 
of value in the differentiation of these mosquitoes or that are essen¬ 
tial to a clear understanding of the relation that these insects bear 


to the transmission of malaria. 

External anatomy. —All mosquitoes are divided into three well 
marked areas for purposes of description: the head, the thorax, and 
the abdomen. 

The head presents upon each side a prominent compound eye, 

the space separating the eyes above being known as the occiput , and 

that separating the eyes in front as the vertex; the back of the head 

is called the nape or neck. The structures of greatest importance 

from a diagnostic standpoint attached to the head are the antenna ? 

and the palpi , for attention to these structures alone is generally 

sufficient to enable one to distinguish between the Anophelince and 

other mosquitoes. The antennce are two jointed structures arising 

from the head and vary in length and structure. In the male they 

are plumose but in the female they are surrounded by hairs, in most 

species, so that the sex of a mosquito is easily determined by noting 

whether the antennce terminate in minute plumes or whether they 

are surrounded by hairs that become shorter as the end of the 

antenna is reached. As only the females suck blood the detenni- 

*/ 

nation of the sex is of importance in any study of the prevalence 
of malaria. 

The palpi , two in number, arise from the head between the an- 
iennce and the proboscis , and are of value in the differentiation of 


PROPHYLAXIS OF MALARIA. 


45 


the Anophelinai , as in this group the palpi are of practically the same 
length as the proboscis and longer than the antenna, while in Culex 
and Stegomyia the palpi in the female are short, club-like structures, 
very much shorter than the proboscis or antenna. As a practical 
working rule it may be stated that any female mosquito having 
palpi approximating the length of the proboscis belongs to the 
Anophelina and, therefore, may be concerned in the transmission of 
malaria. 

The proboscis , or sucking and piercing organ, is a complex structure 
arising from the head between the palpi. It consists of seven parts, 
the labrum, the epipharynx, the hypopharynx, two mandibles or 
lancets, and two maxillae, which, when the insect is not biting, are 
all inclosed in the labium. All of the mouth parts originate beneath 
the clypeus , a chitinous prolongation of the anterior portion of the 
head. At the base of the hypopharynx is situated the so-called 
salivary pump in which the salivary duct empties and is continued 
beyond it into the hypopharynx. The action of this pump is to 
draw the saliva from the salivary glands into the pumping organ 
after which it is forced into the channel along the hypopharynx. 
The saliva is injected into the wound when the mosquito bites and 
with it the malarial sporozoites if the insect is infected. 

The thorax .—The thorax is situated between the head and abdomen 
and is composed of the mesothorax , the scutellum , the prothoracic 
lobes, and the posterior portion, or metathorax. It contains the 
salivary glands and is of importance to entomologists in the classi¬ 
fication of mosquitoes, because of the character of the scales which 
cover it. The legs arise from the thorax, and are six in number, 
and the two icings arise from the upper portion of the thorax and 


their venation is of great importance in classification. 

The abdomen. —The abdomen consists of 10 segments, the posterior 
two being much smaller than the others and containing the sexual 
organs. The scales that cover the abdomen in most species are of 
considerable value in classification to the systematic entomologist, 
as they vary greatly in shape and arrangement. 


The internal anatomy of the Anophelina .—The alimentary canal 
of mosquitoes is divided into a fore-gut , a mid-gut , and a hind-gut. 
The fore-gut lies in the head and thorax and consists of the mouth, 
the pharynx, and pumping organ, the esophagus and the esophageal 
diverticula. The mid-gut begins in the thorax and extends from 
the esophageal diverticula to the hind-gut, filling most of the 
abdominal cavity. It consists of the so-called stomach and the 
pylorus. The portion of the mid-gut known as the “stomach” is 
of special interest to the student of malaria prophylaxis, for it is in 
this portion that the mosquito cycle of the malaria plasmodia begins, 
the ookinete produced by the fertilization of the female plasmodium 


46 


PROPHYLAXIS OF MALARIA. 


bv the male penetrating the wall of this portion of the intestinal 
canal and forming the cyst in which are produced the sporozoites. 
This portion of the mid-gut lies at about the level of the sixth ab¬ 
dominal segment. 

The hind-gut begins at the pyloric dilatation into which open the 
five Malpighian tubes and ends at the anus. It consists of the 
pyloric dilatation, the ileum, the colon, and the rectum. 

The genital organs , while of great importance to the entomologist 
in the classification of species, will not be described, as they can not 
be used for this purpose by the ordinary observer. 

The salivary glands .—The salivary glands are situated in the ante¬ 
rior portion of the thorax and are of interest because it is through 
them that the malaria sporozoites reach the mosquito’s proboscis 
and eventually the blood of man, being injected into the wound when 
the insect bites. The glands are two in number, each consisting of 
acini lined with large granular cells and possessing a central duct 
which unite, after leaving the acini, to form a common salivary duct 
which enters the alimentary canal close to the base of the proboscis. 
It is in the cells lining the tubular salivary glands that the malaria 
sporozoites are found at the termination of the cycle of development 
of these parasites in the mosquito. 

The life-cycle of the Anophelince .—The Anophelince , in common 
with all mosquitoes, passes through larval and pupal stages before 
development into the perfect insect and these stages are aquatic so 
far as we know. 

The ova .—The ova of Anopheles are generally laid upon the sur¬ 
face of water but a few species will lav them in wet ground, as I 
have observed in the Philippines. The eggs are not laid in boat¬ 
shaped masses, as in the case of the common Culex mosquitoes, but 
singly, and by adhering end to end geometrical patterns are some¬ 
times produced that are quite characteristic. The distinguishing mark 
of the eggs of the Anophelince is the presence of the so-called “ float,” 
a hydrostatic organ composed of a partial envelope expanded along the 
middle of the egg. giving it a very characteristic appearance. These 
lateral floats are, variously marked in the eggs of different species and 
vary in size but are always easily distinguished and of the greatest 
service in differentiating the anopheline egg from that of other mos¬ 
quitoes. The eggs are oval in shape and eggs hatch, in most species, 
in from one to two days, but this varies so much with external condi¬ 
tions and with the different species that a general statement is hardly 
justified. From thirty to over a hundred eggs may be deposited by a 
single female. 

The eggs will remain alive in moist mud for considerable periods 
of time, even as long as 6 days, but can not resist complete drying for 
over 12 hours, so far as is known. This fact is important, as it indi- 


Bulletin No. 6, Medical Department, U. S. Army. 



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PLATE 9. 



Egg raft. Culex territans Walk. 


After Howard 



After Howard. 



After Howard. 


Egg. Stegomyia fasciata. 


Egg. Anopheles crucians. 

























































































I, 





















































































PROPHYLAXIS OF MALARIA. 


47 


cates that drainage of pools or other small collections of water will 
not be efficient if the mud remains moist until water again gains ac¬ 
cess to the pool. The observations of Nuttall and Shipley 11 and of 
Christophers and Stephens , 12 as well as others, prove conclusively 
that the eggs of the Anophelinee will remain alive in moist mud for 
days but that in dried mud they quickly perish. 

The larvae .—The larvae of the Anoplielince are distinguished from 
the larvae of other mosquitoes by the elongated, comparatively narrow 



Fig. 2.—Larva of Anopheles and Culex. 1,Larva of anophelinse. Note horizontal posi¬ 
tion in relation to surface of the water, and the absence of syphon (A). 2, Larva of 

Culex. Note angular position in relation to surface of the waiter, and presence of the 
syphon, at A. (Fig. 1, after Howard; 2, after Theobald.) 

head and the absence of the respiratory tube or siphon. Like the 
adult insect the body is divided into three portions—the head, the 
thorax, and the abdomen. While in the ordinary Culex mosquitoes 
the head is comparatively broad, in the anopheline larvae it is narrow 
and elongated and easily distinguished. The important differential 
point, however, is the great difference in the breathing apparatus, 
the long respiratory tube of Culex and Stegomyia being replaced by 
openings in the eighth abdominal segment, which, while slightly 
raised, force the larvae to lie parallel with the surface of the water. 
The long respiratory tubes of all other mosquitoes allow them, when 
breathing, to suspend themselves at an angle with the surface of the 














48 


PROPHYLAXIS OP MALARIA. 


water, but owing to the absence of the respiratory tube in the Ano- 
phelince the larvae always lie horizontal to the surface. This fact 
makes the differentiation of these larvae very easy, but, as Ludlow 13 
has pointed out, other aquatic larvae have this peculiarity, so that 
one must be familiar with mosquito larvae before concluding that 
anophelines are present. 

The larvae vary in color, but are usually gray or brownish. They 
molt four times before becoming pupae, and the length of this stage 
of development varies greatly, the average probably being from 10 
to 14 days, although it has been observed to be as*short as a week 
and as long as 30 days. It varies with different species and with 
external conditions. 

The pupce. —The pupal stage of development is probably the 
shortest, averaging about two days, but varying between two and 
six days according to temperature and other external conditions. 
The pupae are not easily differentiated from those of other mosqui¬ 
toes, and, therefore, will not be described. 

The adult mosquito or imago. —After a period of development 
varying in time, but usually in from two to four days, the pupa 
rises to the surface of the water, remains there, and the skin over 
the thorax breaks open and liberates the adult insect. This process 
has been very accurately described by Hurst 14 , to whose work the 
reader is referred. 

Habits of mosquitoes of importance in the prophylaxis of mala¬ 
ria. —A knowledge of the habits of the larvae and the adult anoplieline 
is of importance in the prophylaxis of malaria, for the better ac¬ 
quainted one is with this portion of our subject the easier will be the 
application of methods looking to the destruction of these insects. 

Habits of the larvae. —I have already spoken of the position of the 
larvae of anophelines being parallel with the surface of the water, 
and this position is maintained unless the larva is frightened, when 
it will sink below the surface. It feeds upon floating objects, which 
are attracted to the mouth by the fringes of the mouth parts pro¬ 
ducing a current toward the mouth. The larvae eat both vegetable 
and animal matter and devour one another. 

The larvae of some species of Anopheles are able to hibernate , as 
shown by the observations of Galli-Valerio and de Jongh. They 
found that the larvae of Anopheles bifurcatus hibernate beneath the 
leaves of aquatic plants, and that they survived even when in water 
between two sheets of ice. 

Of the natural enemies of mosquito larvae may be mentioned the 
fresh-water hydras, many aquatic insects, salamanders, and certain 
species of fish, to be hereafter considered. 

Habits of the adult anopheles — Feeding. —The feeding habits of 
the species of anophelines that frequent the habitations of man are 


PROPHYLAXIS OF MALARIA. 


49 


of importance in prophylaxis. It may be stated that while many 
species of anophelines are of sylvan character, all of the species that 
have come in contact with man and have continued in association 
with him are bloodsuckers, and that, even in the sylvan species, 
blood is a normal food, being obtained from other animals than man. 
It is not true that a meal of blood is necessarv to the female before 
depositing her eggs or, as has been stated, that the fertilization of 
the female is impossible unless she has sucked blood. Grassi found 
that Anopheles will bite large animals in preference to small ones—a 
horse being bitten in preference to a man—and that they bite in 
the open as well as in habitations. The first meal of blood is taken 
two or three days after the insect emerges from the pupa, as shown 
bv Darling and Grassi, and thev will bite at intervals of a few hours. 

It is well known that during rains it is seldom that one is bitten 
by anophelines, but that after the cessation of the shower they are 
very vicious. This is especially noticeable in the Tropics during the 
rainy season. The effect of temperature upon the feeding habits is 
also very marked, a high temperature apparently stimulating the 
biting propensities of most species of anophelines. 

The time of day in which the anophelines bite is an important pro¬ 
phylactic point. Most species of the Anophelince fly during the 
twilight hours, and it is during this time that one is most frequently 
bitten. While this is true, I have seen various species of Anopheles 
biting in the late afternoon, and M yzomyia funesta , a common ma¬ 
laria mosquito, biting in the early morning and even at noon in 
the Philippines. 

Anophelines will bite during the night if the temperature is high, 
as in the hot portions of the Middle West, but where the nights are 
cool, even though they may be present in great numbers, they bite 
only during the twilight hours and in the early morning. A beau¬ 
tiful illustration of the twilight habits of the anophelines is noted 
in the observations upon the Canal Zone regarding the flights of 
Anopheles , in which it was found that the flight of these insects from 
the propagation area to the town began about 6.30 in the evening 
and that it ceased before 9 in the evening, while the return flight 
began at 6 o’clock in the morning and lasted about half an hour. 

After biting, the anophelines usually hide out of doors, within a 
short distance of habitations, beneath tall grass, or within the foliage 
of bushes and trees. However, they often remain within the habita¬ 
tion, and I have observed hundreds of anophelines in the daytime 
around the baseboards of toilet sinks and upon clothing in dark 
closets in the Philippines. 

While, as has been said, most anophelines prefer the twilight 
hours for biting, they will bite at any hour of the day. Chagas and 
Neiva l5 , Smith 10 , and Howard 17 all have recorded distances in which 
58000°—14-4 



50 


PROPHYLAXIS OF MALARIA. 


biting occurred during the middle of the day, in the sunlight, but 
prophylactic measures based upon the twilight habit would prevent 
the vast majority of bites. 

Flying distance .—In most of the older publications dealing with 
mosquitoes it is stated that they do not cover great distances in flight. 
This statement, in the light of our modern researches, can no longer 
be considered correct, even in regard to the Anophelince . In 1900 18 ,1 
published a statement that from personal observations I believed that 
certain species of Anopheles often flew from 2 to 24 miles in order 
to reach the post where the observations were made, and this state¬ 
ment, being so much at variance with generally received opinions 
regarding the flight of anophelines, was subjected to much criticism 
by entomologists. Since then my observations have been confirmed 
by workers upon the Canal Zone and by James and Christophers in 
India 19 , as well as others, and it is now well recognized that while 
anophelines prefer to breed near their prey, they will fly long dis¬ 
tances in order to lay their eggs or to feed, provided there are no 
breeding places in the near vicinity. 

The experiments of the department of sanitation in the Canal Zone 
in regard to the flight of anophelines are of special interest and value. 
In their report they say 20 : 

Adult anopheles were stained with dye and liberated at the swamp. Subse¬ 
quently some of them were collected on the opposite side of the river, at the 
locks, and in houses 4,700 feet from the liberating station. It should be stated 
that the anopheles’ flight was decidedly marked and was easily noted by half a 
dozen witnesses, when their attention had been drawn to it. Even so, not one 
person in areas thickly infested did note the flight until shown the way to ob¬ 
serve it. 

Regarding the flight of the anopheles the report states: 

The flight was from west to east and quite marked. As it became darker the 
quantity of flying anopheles increased, and by looking at a dark object against a 
clear sky hundred of anopheles could be seen passing by. 

The mosquitoes flew from the propagation area in a swamp to 
Gatun, and some of the breeding places were more than 2 miles from 
Gatun. 

At Mian Mir, James found adult mosquitoes present when no 
larvae could be found within 2 and 2J miles, and Le Prince 21 deter¬ 
mined that Cellia ( Anopheles) alhimanus , the principal transmitter 
of malaria in the Canal Zone, will travel against a 4-mile breeze for 
distances of a mile, and possibly farther. 

The confusion regarding the distance of flight of anophelines is 
undoubtedly partly due to observers studying different species, but 
while it is probably true that the majority prefer to fly short distances 
in order to reach their food, it must be recognized that these mos- 

■ . ••••'• - • ...JOi. 

quitoes are capable of flying for two or more miles, and this fact 


PROPHYLAXIS OF MALARIA. 


51 


is of great importance in the prophylaxis of malaria. It is more 
than probable that much longer distances can be covered by inter¬ 
rupted flight, and that the anophelines are not an exception to the 
rule that mosquitoes will fly for great distances in order to reach 
their food or their breeding places. 

Breeding places .—Contrary to our older notions regarding the 
breeding places of anophelines we now know that these mosquitoes 
may breed in practically any collection of water, even though there 
be quite a current present. Watson 22 , in the Federated Malay States, 
found that N yssovhynchus willmori will breed in mountain streams 
where the current is swift, and that the larvae of this species is capa¬ 
ble of swimming against the current of these streams. As a rule 
the anophelines prefer to breed in comparatively clean water, as 
that found in slowly running streams or in pools of rain water, 
but they will breed in foul water and have been found in sewers. 
Paddy fields, storage tanks, wells, ditches, ponds, gutters, drains, 
and springs are all favorite breeding places of anophelines, gome 
species preferring one place and some another. As Theobald states: 

Practically all kinds of collections of water are acceptable to the larvae; 
some prefer rain-water barrels, cisterns, and the water in tins, calabashes, 
and jam pots; others ponds, slow running streams, and along the banks of 
large rivers: others live in the water collected in bromelias, and in the water 
that collects in hollow bamboos, gaining their entrance through exit holes 
left by boring insects. The domestic species which are best known usually 
choose barrels and cisterns. 

In the Philippines a favorite breeding place of anophelines was 
the cavity left after cutting off bamboo poles near a joint. In the 
latter part of the rainy season I have found larvae in nearly every 
bamboo pole examined, and at Camp Stotsenburg, where temporary 
quarters for a large number of troops were built of this material, 
anophelines became a veritable scourge and malaria increased to 
such an extent that it was found necessary to remove the larger part 
of a brigade which had been stationed there. 

Among the breeding places of anophelines which are most likely 
to be overlooked may be mentioned the small depressions in the 
ground produced by the hoofs of animals or the inequalities left in 
plowed land. In the tropics, during the rainy season, such breeding 
places are sometimes very numerous and furnish a considerable pro¬ 
portion of the mosquito population. Another source of mosquitoes 
nenerallv overlooked is the water that collects at the bases of the 
leaves of certain plants, especially the Bromeliacece. Lutz 23 found 
Anopheles cruzii breeding in the water collected by the leaves of 
these plants and other observers have confirmed his results. 

It has also been determined that some species of Anopheles will 
breed in brackish or salt water. Among these species may he men- 


52 


PROPHYLAXIS OF MAI.ARIA. 


tioned Anopheles crucians , Myzomyia ludlowii , Anopheles quadri- 
macutatus , Cellia ( Anopheles ) alhimanus , Cellia ( Anopheles) ary y- 
ritarsis , and Anopheles tarsimaculata. 

From this very brief discussion of the breeding places of the 
Anophelince it is evident that in malaria prophylaxis the practical 
point to remember is that no collection of water, however minute, 
should be considered as of no importance as a breeding place for these 
insects. As Smith has well said, the Anopheles breed “ everywhere ,” 
and therefore every collection of water should be carefully examined 
before it is considered free from the larvae of these insects. 

Certain colors in relation to the Anophelince .—It is a well known 
fact to anyone having experience with mosquitoes. that they prefer 
dark to light colors and that a person dressed in black is much more 
apt to be bitten repeatedly than a person dressed in white. The re¬ 
searches of Nuttall and Shipley 24 have shown that A. maculipennis 
is very partial to certain colors, and this is probably true of other 
species of anophelines. They found that dark blue was the most 
attractive color to them and that pale green, light blue, orange, and 
yellow actually appeared to repel them. They call attention to the 
khaki uniform as especially suitable because of its lack of attraction 
for the insects. 

Longevity and- hibernation .—Our knowledge regarding the longev¬ 
ity of the Anophelince is still incomplete, but we know that the life 
of the male is only a few days and that the females of different 
species vary greatly in length of life, some living for weeks only, 
while those that hibernate may live for many months. 

In temperate climates the winter is passed by most anophelines in 
the adult stage of development, the females alone hibernating. 
Although this is so, the anophelines may pass through the winter 
in the ova or as larvae. The females that hibernate are fertilized, 
and only lay their eggs in the spring, although if a warm spell 
occurs during the winter some of them will emerge from their bid¬ 
ing places and bite, and may thus cause outbreaks of malaria even 
in the middle of winter. 

In the Tropics the adult anophelines hibernate during the hot dry 
season and lay their eggs at the beginning of the rainy season. As 
long as the weather is dry very few anophelines will breed in the 
Tropics, but the beginning of the rainy season is always marked by 
an immense increase in the number of these mosquitoes, and breeding 
places are easily found. 

During hibernation the adult insects may be found in cellars, out¬ 
houses, stables, under the roofs of unceiled habitations, in dark 
closets, in hollow trees, or under shelving. In these situations they 
may be found in hundreds, or even thousands, and if disturbed 
appear sluggish and only fly for short distances. 


PROPHYLAXIS OF MALARIA. 


53 


I have already called attention to the fact that the ova of anophe- 
lines will withstand drying for some time, and I am of the opinion 
that in the Tropics many species would cease to exist were it not for 
this property, owing to the long dry season and the comparatively 
small number of hibernating females. 

As regards the number of generations during a season our knowl¬ 
edge is very incomplete. According to the observations of Kulagin 25 
the anophelines have only one generation annually. He calls atten¬ 
tion to the fact that the female anopheline does not lay her eggs all 
at one time and states that, in temperate regions, the egg-laying ex¬ 
tends throughout the entire summer, and that the adult mosquitoes 
derived from these eggs do not lay eggs until the following year. 
His observation^ extend over sev¬ 
eral years and are the most ac¬ 
curate that we possess upon this 
subject. 

Nothing is known regarding 
this subject in respect to the mos¬ 
quitoes of the Tropics. 

Resting position of adults .— 

The resting position of adult 
anophelines and the position as¬ 
sumed when biting, the two be- 

Cz 7 

ing practically identical, offers 
one of the easiest and most valu¬ 
able methods of differentiating 
between them and other mos¬ 
quitoes. When resting upon a 
flat surface, as a wall, mosquitoes 
belonging to the Anophelinaz , 
with few exceptions, form a dis¬ 
tinct angle with the surface, the 
insect resting upon the first two pairs of legs, the last pair floating in 
the air or held out straight behind it. The angle formed by the body 
of the mosquito and the surface varies, but sometimes is nearly a right 
angle. The only exceptions to this rule among the anophelines 
commonly observed is J [yzomyia ( Anopheles ) culicifacies , which 
rests upon a surface in the same position as a Culex mosquito, and 
Pyretophorus ( Anopheles) superpictus and Myzomyia ( Anopheles) 
hispaniola , which assume a perpendicular position in reference to the 
wall. 

The position assumed b}^ other mosquitoes, as Culex , Stegomyia , 
etc., is well described as u humpbacked,” the abdomen approaching 
the resting surface while the thorax is distinctly higher than any 
other portion of the body, thus giving the humped appearance. 




Fig. 3. —Comparison of resting position of 
Anopheles and Culex. 1. resting posi¬ 
tion of Culex, on vertical surface; 2, 
resting position of Anopheles on vertical 
surface. (The resting position upon a 
horizontal surface may be observed by 
turning the page so that the vertical 
line becomes horizontal.) 





54 


PROPHYLAXIS OF MALARIA. 


Whatever the position of a mosquito, it can always be determined 
whether it is an anopheline by attention to the relative position 
of the proboscis to the body. In the Anophelince the, proboscis is 
always in a direct line with the rest of the body when the insect is 
resting upon a surface, while in all other mosquitoes the proboscis 
forms an angle with the abdomen. This peculiarity is easily recog¬ 
nized and gives the anopheline a distinctly “business-like" appear¬ 
ance, the entire body of the insect resembling a boring instrument. 

Practical points in the differentiation of the Anophelince. —The fol¬ 
lowing practical points may prove of use in the differentiation of 
anophelines from other mosquitoes in their various stages of develop¬ 
ment : 

1. The ova. —The ova of the Anophelince are hever found in 
masses, but are laid single upon the surface of the water, the ends 
often being connected, thus forming geometrical patterns. They are 
further distinguished by the possession of lateral “floats," which 
never appear on the ova of other mosquitoes. 

2. The larvae. —The larvae of the Anophelince are easily distin¬ 
guished from those of other mosquitoes by the absence of the long 
respiratory tube or siphon. Because of this the anopheline larva is 
compelled to lie parallel with the surface of the water, while other 
mosquito larvae hang head downward at an acute angle with the 
surface of the water. In addition the small, narrow head of the 
anopheline larva distinguishes it from other mosquito larvae. 

3. The imago or adult. —The following points distinguish the 
adult anopheline from other adult mosquitoes: 

a. The relative length of the palpi and the proboscis. —In the 
Anophelince the palpi of the female are as long as the proboscis, 
while in other mosquitoes the palpi are much shorter than the pro¬ 
boscis. The males are distinguished from the females bv their 
plumose palpi. By attention to this simple detail any mosquito may 
at once be placed so far as its relation to the Anophelince is concerned. 

b. The angle of the proboscis with the body. —The proboscis in 
the anophelines never forms an angle with the rest of the body but 
continues in a direct line with it, as already stated. 

c. The resting position. —When resting upon a surface most of the 
Anophelince form a distinct angle with the surface, while other mos¬ 
quitoes appear humpbacked owing to the fact that the abdomen is 
nearer the surface than the thorax. 

cl. The spotted wings. —Most of the Anophelince have spotted wings 
and while some other mosquitoes also present spots upon these struc¬ 
tures it is a good practical rule to always regard with suspicion any 
mosquito having spotted wings, as the chances are altogether in 
favor of its being an anopheline. 


Bulletin No. 6, Medical Department, U. S. Army. 


PLATE 10. 



ANOPHELES AND CULEX LARV/E IN NATURAL POSITION IN WATER. 

(HOWARD.) 



FEMALE ANOPHELES IN CHARACTERISTIC STINGING POSTURE. 

Photograph of the model (X 75) in the American Museum. Magnification of figure about 10 

diameters. 









PROPHYLAXIS OF MALARIA. 


55 


METHODS OF COLLECTING AND DISSECTING MOSQUITOES. 

The following directions for the collection and dissection of ano- 
phelines are all that are necessary for one engaged in practical 
prophylactic work. No attempt is made to describe methods of 
breeding the insects or of experimentation, as these phases of the 
subject relate more distinctly to the laboratory than to work in 
(he field. 

Collection ^—The ova of the Anophelince may be collected from the 
breeding places with a white agate ware dipper, but it should be 
remembered that they are very inconspicuous and have to be searched 
for very carefully. 

The larva?, may be collected in a dipper from the breeding places 
by slightly muddying the water of puddles or shallow streams when 
thev are more easily observed bv reason of their grayish color. In 
small receptacles, water barrels, etc., they can easily be collected with 
the dipper. The adult insects are easily captured by the use of a 
collecting tube. At night they may be attracted by placing a lamp 
in such a position that a portion of the wall is but slightly lighted, 
when it will be found that the mosquitoes gather at the junction of 
lhe shaded area and can be easily captured. For this purpose a large 
test tube or a small straight glass cylinder may be used, the open 
end being placed over the mosquito as it rests upon the wall, then 
slightly moved across the surface of the wall, when the insect will 
fly to the closed end, whereupon the open end is removed quickly 
from the wall and plugged with cotton. If it is desired to kill the 
insects a small amount of cotton saturated with chloroform is placed 
at the bottom of the tube and covered with a disk of perforated card¬ 
board. after which the tube is used as described. The utmost care 
should be used to avoid breaking the wings or otherwise injuring 
the insects if they are to be sent away for identification. 

As the identification of the species of mosquitoes in any region 
may be a matter of great military importance, every effort should 
be made by medical officers to have the species identified in the 
localities in which they are serving. For this purpose the chloro¬ 
form killing tube should be used to capture the mosquitoes, after 
which they are carefully slid from the tube into a small box con¬ 
taining absorbent cotton. Great care should be taken to avoid touch- 
ing the insects or allowing the chloroform in the killing tube to come 
in contact with them. Not more than three or four mosquitoes 
should be placed in a box, and a label should be pasted upon the 
cover giving the place, date, and hour of collection, and any other 
data that is thought useful. If the box is to be mailed it should be 
inclosed in a larger box and packed carefully in cotton. 


56 


PB0PIIYLAX1S OP MALARIA. 


The dissection of mosquitoes .—To many the thought of dissecting 
a mosquito conjures up an amazing amount of difficulty, largely 
owing to the small size of the object to be dissected. As a matter 
of fact anyone possessing the most rudimentary knowledge of labo¬ 
ratory technique should have no trouble in dissecting these insects 
and demonstrating the presence or absence of malarial infection in 
them after having once been shown the really simple technique. 

In order to make good dissections the following apparatus is 
necessary: Microscopic slides and cover glasses, fine dissecting 
needles, a good dissecting microscope, and some normal salt solution. 
A compound microscope, of course, is necessary for studying the 
development of the malaria plasmodia, but malarial infection of 
the mosquito may be demonstrated, in many instances, with the high 
powers of the dissecting microscope. The parts of the mosquito of 
special interest to one engaged in the prophylaxis of malaria are the 
salivary glands and the portion of the mid-gut of the mosquito 
known as the stomach. 

Dissection of the salivary glands. —To make a perfect dissection 
of the salivary glands of the mosquito requires considerable skill, 
but it is comparatively easy to secure portions of the glands suffi¬ 
ciently perfect to allow of demonstrating the sporozoites. 

The salivary glands are situated within the thorax, lying ventrally, 
commencing at the posterior portion of the neck and ending at the 
level of the first pair of legs. The simplest way of securing them 
for examination is to cover the insect with salt solution and place 
it upon the stage of the dissecting microscope in such a position that 
the head is toward the dissector's hand. Then, with the needle in 
the left hand steadying the thorax, the chitinous covering of the 
thorax just back of the neck is incised, and then gentle traction is 
made with the needle in the right hand upon the head, separating it 
gently from the body. If the operation has been successful it will 
be noted that a minute bit of white tissue has been extracted with 
the head, and upon examination with the compound microscope it 
will be observed that in this bit of tissue lie the salivary glands, or 
portions of them. This tissue should now be removed from the head 
with a fine needle and placed upon a microscopic slide in a drop of 
normal saline. 

In order to determine the presence of malaria sporozoites the 
preparation should be covered with a cover glass, gentle pressure 
applied, and examined with a one-sixth inch or one-twelfth inch 
objective. If sporozoites are present they will appear as fine, hyalin, 
curved rods, lying within the cells or ducts of the gland or free in 
the salt solution in great numbers. They often occur in masses or 
side by side and measure about 14 micros in length. 











Bulletin No. 6, Medical Department, U. S. Army. 


PLATE 11. 



TYPICAL ANOPHELINE MOSQUITO. 
Note long palpi and spotted wings. (Ludlow.) 

















Hu . - . /« in, / 


l'i /II I'/ 



I Yf'ICAl /.hi K, 1111 MO'iQUI I 1 1 

ll'tlh ".Il'/M |< «I |,l IU,/| 1/(1//Id;/ II d'lld// ; 









J'l,'Of'H VI A / I i oi vl a I A lrl a 


57 


bikHfrl.ion of the ' nlomor.lt, of I hr, m,o,o/iolo. 1 o rji •-.not t.fi ;j f 
portion of tin- mid j/ut of tin? rno/jiiito. kr/i ;>-. tin? ' .-.tornado 
till’ following ft! <><H<ltirc. I ■: iW/fl 11 Kli'til l<’i J 

Tin- m- w t, from wliidi tin* winjs-i ;j r>d k?#.? h.ivn la*/?n r<*mo'/<?d by 
' I or : I . moi t 4 f,<•/j with a littk? a Irobol or -.alt volution ami tfn?u 
J bade downward upon tin- |/lo f.np of tin- di n/linj/ rnir.ro 
/opr or upofi a ^lfr--.fi Jid<• pkn/*d upon tin? -tn^r I'hinpr a ru*?/jk? 
in tlif left Ini ml to r.trady tl»<* in rot. .1 oink in rnadr. in tfn- dbtin of 
tin tliof ;i x Ofj <-ilJn-r -.nl<- ;j rn-ar tfn- po ■-.».<? r ror <-r,d -j jn/ -ibk? t. n 
k-ft rn-rr 1 Ir )•-. fiow plarrd firmly upon tin? tboraz .onJ tin? rij/bt ,pon 
tin- In t a bdorninaI .rj/mrnl r 1 d [/rntk t.rartion rxrrtrd by tfn-. n#ht 

band, wln-n brtv.rrn tfn- -.rparatin# .rj/rnrnP ,1 /lot/? m>» of .j /nr a 
i.ob/rvrd n lin fi r-ontiiin tfn- find gut. forni gut Malpighian t At .In-, 
urnl ovarir*., or may r/mtam only -1 portiori of tin-r I fin mid gut 
I-, rpnratrd, and will br found to rom-.r-.f. of nr; antrnor tubular uor 
lion m ml n po tnrior -.arulnr portiori v/bnb i-? f.f,<? -•/> r*Jh?d torn 
in-li of tfn- rno/juito and v/bidi contains tin? malarial ry.?tor 

f/ffofon if tfn-y f/< prr-/nt f lu-, portion of tfn- rnn! gut i fdarrd 
upon » -lido nrnl nxnrninnrj with n orn* ;?jxtf> Inn-.: but if it '/mtain? 
blood if hould fin, dr--/ nr drd a-. ir; tin -. ' n -/? tfn- zyfjot.*,n arr n ot to nr 
over looknrj 

If tfn- fully dovr.loprd r:yarr pr<?--•/?nt. tin?;/ may fn? -/*/?n ofii tfn? 
orn- ixffi lm •-. [nojrr.ting from tfn- wall of tfn- tornnof* or appar 
rntly rrnbrddrd in ffn- wall, I bry rnn / oftrn fn- pn-.krd >p 'pn;k>y 
by att/ntion to tin-. prr-.rnor of pigmnnt. for --/>mr of tfnrm contain 
a .mall amount of melanin 'I In? ‘-arhr-.t. ?tag<? of/--/?r vr/J r? an oval 
0/ •-.pln-r n-.j I body nf»out k rnn?ron--. ir; ri in rrn-M-r ,j/nJ r/rM n ir*ir;j/ mor<? 
or k j;i['nn-.r/t wbnb rimy 01 rnny- not o<? rnotik /. tf.n zyyoin r 
irnrr-n /- in --.i/n. ,) vo-JJ rJdinf'/J cafi^.uk? r, r oynt //aJJ 'k-'/dop# 
wln-n fin- >•.i>(>ro:.oiIr* f,,» <• rk-v<- \o\>i'i\ ffn-’/ rriny fa? •-/?<• r; par:kir.j/ fin- 
< ? y 0 f. •.. wbnb lmv<- b<-rorrn- -•/; In r [,'<• tf»nt tfn?/ rnn / fa? o" /••/•; o.. 

a r,r)<- f.f»irrj irn fi k-rr I In- pij/rrn-rit 'Worn-/?-•? ;r* amount n tfn 
ygatei dl dop And ■- In-n tbny -irr- full*/ d^nliifa-/) rr;/ir»v f tfn?rn 
mi- rntimly rk-yonl </f [ii[/rrn-r»t 

|*or a morn mirnitn r|n /-r 1 ption of tfn- M'/:f f nio n- r,f i,o<? «?^arr>.r,atJor- 
<if mo---/[uif/a? nrnl r^f f.fo- rr*r/r pboJo^ry of tfn- r/i/ilarra [iln .rrnal.n 
witliin tin- mo-/jfrif/i tin* r<-nrj<-r i.-. w.fwiwl to any of tfn- Jarprnr 
work--, upmi tin- malarial frvrr -. //fjufj ,jr<? p'r*/<•/, ir* tin? b-.t of rofor 
i-iim- . iri tfii-i bullntirr. 


Chapter III. 


PROPHYLACTIC METHODS BASED UPON THE DESTRUCTION OF 

MALARIA MOSQUITOES. 

In the prophylaxis of the malarial infections the following meas¬ 
ures have been found efficient in practice: 1. The destruction of 
the mosquitoes transmitting the infection; 2. The protection of man 
from the bite of mosquitoes; 3. The destruction of the malaria 
plasmodia while in the blood of man. Theoretically, any one of these 
methods would be sufficient to prevent malarial disease could it be 
applied in an ideal manner, but practically, it is but seldom that 
one is successful without the aid of the others, and it is generally 
necessary to combine them all in order to achieve the fullest success 
in the prevention of malaria in any locality. 

In this chapter will be considered those methods of malaria pro¬ 
phylaxis that depend for their success upon the destruction of the 
mosquitoes transmitting the disease, and in applying these methods 
it is necessary that one have knowledge of the life history of the 
Anopkelincp, to the extent comprised in the data given in the pre¬ 
ceding chapter. It is obvious that before applying most of the 
methods mentioned in this chapter it will be necessary to make a 
mosquito survey of the locality one is working in, thus determining 
whether malaria mosquitoes are present or not, their breeding places, 
and the preventive methods most applicable and economical for the 
region investigated. 

The prophylaxis of malaria by the destruction of mosquitoes is 
the ideal method of prophylaxis where conditions are such as to render 
the destruction of these insects practicable, but in the military service 
such methods must necessarily be restricted to more or less permanent 
camps or to permanent posts, as most of them are impracticable upon 
the march or in camps of short duration. In many regions in the 
United States where military posts are located it is believed that the 
malaria present could be entirely eradicated by the adoption of meth¬ 
ods looking to the destruction of mosquitoes, and this may also be 
true of isolated instances in our tropical possessions, but in most 
regions, especially in the Tropics, the most that we can hope to accom¬ 
plish in the way of mosquito destruction is to greatly reduce the num¬ 
ber of the insects, and in such localities other methods of prophylaxis 
must be used in conjunction with the destruction of the mosquito. 

58 


PROPHYLAXIS OP MALARIA. 


59 


The malaria mosquitoes may be destroyed at any stage in their de¬ 
velopment, but most of the prophylactic methods depend for success 
upon the destruction of the insect during the larval and adult stage, 
the larvae being destroyed by the abolition of the collections of water 
in which they have developed or by larvacides, and the adult insects 
by various chemical agents or other measures. The most important 
measures consist in the abolition of the breeding places of the mos¬ 
quitoes by leveling, drainage, and clearing, and if they can be carried 
out in an efficient manner they are the most valuable that we possess, 
and in the vast majority of instances are capable of geatlv reducing, 
if not almost eradicating, malarial disease. Unfortunately, the ter¬ 
rain often renders the application of these measures very expensive 
and other prophylactic methods are substituted, but, where it is pos¬ 
sible, I believe that these measures, although the first cost may be 
great, should be the ones adopted, as they produce permanent results 
and in the case of many of our Army posts would banish malaria 
from the sick report. 

Drainage .—If possible all large breeding places of mosquitoes 
should be drained, if they can not be filled in or otherwise abolished. 
If filling in is feasible, this is the better method, but the relative cost 
of the two methods must be considered for each localitv and the 
choice made as to which will be the cheaper and most efficient. 

If drainage is decided upon, the question arises as to the particular 
kind of drainage to be used. In many temperate and subtropical re¬ 
gions open ditches may be used, provided the edges are kept free from 
plants and algae and there be enough slope to give a compara¬ 
tively swift current. Otherwise, the open ditch, although it may 
drain a larger body of water, simply becomes a mosquito breedery, 
and this is almost sure to happen in the Tropics, where it is practically 
impossible to prevent the growth of plants and algae in the water of 
the ditch. This fact has been well brought out by Le Prince 26 , who 
says: 

On the Isthmus and probably throughout the Tropics, under average conditions, 
we could not consider such a mode of procedure (the open drainage ditch) as 
it would give most unsatisfactory results. Such a ditch would become a ver¬ 
itable Mecca for anopheles. 

In order to prevent the development of vegetation in the ditch it 
would have to be cleaned out in the Tropics on an average of once 
a week, and this alone would make their use practically impossible, 
as the cost of labor and upkeep would be too great unless the ditches 
were few in number and of limited extent. 

The blind drain .—Le Prince, 27 the chief sanitary inspector of the 
Isthmian Commission in 1008, recommends this method of drainage 
in case tile drains can not be obtained. He defines a blind drain 
u as a miniature culvert covered with field stones,” and states that 


60 


PROPHYLAXIS OP MALARIA. 


they give fairly good results. Such drains are constructed as follows: 
A ditch is dug and the bottom covered with flat stones, the sides are 
formed by a layer of flat stones, and a cover stone is placed on top, 
after which the whole is covered with quite large stones and lastly 
with small stones. Regarding this type of drain Le Prince says: 

Where plenty of stone is available and must be removed from a field, this 
form of ditch is economical to make and, in the Tropics, much more economical 
to maintain than an open ditch is, while anopheles larvae do not occur 
therein * * *. We opened some of these drains when the flow of water in 

them was sluggish, but found no mosquito larvae therein. The advantage of 
this type of drain is that there is no first cost for material, the field stones are 
disposed of, and there is no cost of maintenance except when the ditch clogs 
up. A good grade is essential for blind drains, and they will stand on a 
fairly heavy grade. 

The cement-lined open drain .—This is the only form of open 
drain that should be adopted in the Tropics, and it should always be 
laid upon a considerable grade. Such drains should be semicircular 
in shape and constructed of stone or brick, lined with cement. If 
laid upon a good grade such drains will keep themselves clean by the 
flushing of the water and will not become filled with vegetation and 
algae. 

Subsoil drainage with tiles .—Le Prince says that “ the use of tile 
drainage is the most economical and permanent method of destroy¬ 
ing anopheles in the Tropics. The work costs from 16 to 20 cents a 
foot upward, according to the depth of the trench, material to be 
excavated, and distance that the tile and covering stone has to be 
carried." He recommends that the tile drains should not be given 
a flatter grade than 0.5 per cent, and states that those having as 
high a grade as 5 per cent gave perfect satisfaction if the tiles be 
covered with plenty of stone to hold them in place. This is the 
method of drainage adopted in the Canal Zone, where it has proven 
less expensive in the end than the open ditch and much more efficient. 

The question of the prevention of mosquitoes bv drainage is a 
purely economical one, as there is no question of its efficiency in any 
region where it can be applied. In the Tropics its application is 
much more difficult than in temperate regions, but the success of 
this prophylnctic method in the Canal Zone proves that even in the 
Tropics it can be used under the most difficult conditions and that 
its use is both economical and successful. In many of our posts a 
system of tile drainage would completely eradicate mosquitoes at a 
much less final cost than is now expended in screening and for 
mosquito nets. 

Filling .—In many localities the filling in of low ground and of 
small pools will serve to destroy most of the breeding places of 
mosquitoes, and this is often a very valuable prophylactic method. 

Removal of shelter .—In conjunction with drainage and filling in 
of the breeding places of mosquitoes, the removal of brush along 


PROPHYLAXIS OF MALARIA. 


61 


the banks of streams and of vegetation and algae in the streams or 
of any shelter for the mosquitoes, such as is furnished by jungle, 
long grass about residences, and vines and bushes, is a valuable pro¬ 
phylactic measure. The removal of the vines so often observed in¬ 
closing the porches of barracks and quarters in some of our most 
malarious posts should be insisted upon if mosquitoes can not be 
eradicated, as they furnish shelter to many of these insects, and their 
removal will result in a great diminution in the number of mosquitoes 
and, consequently, in the prevalence of malaria. The same is true 
of all shrubbery about habitations, and the measure adopted in the 
Canal Zone of removing all such vegetation for 200 yards around 
the houses could be followed with excellent results in more than one 
of our Army posts. 

The clearing of rank vegetation and jungle for several hundred 
yards around a camp or post is not only useful because it deprives 
the mosquito of shelter, but it also results in the discovery of the 
small breeding places of the mosquitoes which could not otherwise 
be seen. The anopheline mosquito does not require a lake to breed 
in but, as has already been stated, will breed in the smallest de- 
pressions in the ground that will hold water, and every clearing 
operation, especially in the tropics, always results in the discovery 
of many of these minute breeding places. 

At Camp Stotsenburg, in the Philippines, it was invariably noted 
that mosquitoes increased greatly in number whenever the grass 
about the post was allowed to grow to any great length and that 
a coincident increase occurred in the number of malarial cases ad¬ 
mitted to hospital. At one time, owing to lack of facilities for 
cutting, the grass was allowed to grow for several weeks, and the 
mosquitoes became so numerous as to be almost unbearable, while 
the number of cases of malaria admitted to the hospital became 
alarming. As soon as the grass was mowed the mosquitoes decreased 
in number, as did the number of malarial infections, thus conclu¬ 
sively proving the danger of affording shelter to the mosquito. 

Destruction of mosquito larvce with larvacides. —While, the drain¬ 
age or filling in of the larger bodies of water that are breeding places 
for mosquitoes is the ideal method of dealing with them, it fre¬ 
quently happens that this is impossible owing to various local con¬ 
ditions. When this is the case the larvae may be killed by certain 
substances which may be added to the water, and this furnishes us 
with a prophylactic method of considerable value. 

Many substances have been recommended for this purpose, the most 
important of which will now be considered: 

Petroleum .—The use of kerosene as a larvacide was first recom¬ 
mended by L. O. Howard, 28 and it has been used very largely by the 


62 


PROPHYLAXIS OF MALARIA. 


Army, both in this country and in Cuba and the Philippines, with 
excellent results. This method of prophylaxis depends for success 
upon the fact that the larvae of mosquitoes are unable to breathe 
if the surface of the water is covered with a film of oil, and it there¬ 
fore follows, that in selecting petroleum for this purpose an oil 
should be chosen that will spread rapidly when placed upon the sur¬ 
face of water and one that will not evaporate too rapidly. Howard 
recommended to the Army in Cuba the use of the grade of oil known 
as light fuel oil, costing from $2.25 to $3 per barrel, and this was 
used with good results. A thicker oil, composed of 4 parts of oil 
of 18° gravity and 1 part of oil of 34° gravity, is recommended by 
Quale, who used it in California and found that it remained efficient 
for from three to four weeks after application. 

The application of the oil, in the case of large bodies of water, is 
best made with a pump having a straight nozzle. The operator is 
rowed from side to side of the pond and the oil discharged at such in¬ 
tervals that when it rises and spreads the entire surface passed over is 
covered. In smaller collections of water an ordinary watering pot 
may be used with a spray nozzle or the oil may be poured from a 
cup or dipper. The greatest care should be taken to see that there 
are no portions of the surface left uncovered after the oil has spread, 
and all oiled collections of water should be inspected at least every 
third or fourth day, as the layer of oil becomes easily displaced by 
currents in the water, by winds, or by the movements of aquatic 
animals. Whenever unoiled areas appear upon the surface the 
oiling of that particular portion of the pond should be repeated. In 
the case of more or less stagnant streams or ditches the oil is best 
applied with a pump and the application frequently repeated. The 
pumps used for this purpose are the ordinary knapsack Dump or the 
bucket pump. 

The exact time that the oil will have to be renewed varies greatly, 
and in many instances the method is rendered almost useless by 
ignorance regarding the necessity of renewing the oil at frequent 
intervals. . While, in rare instances, one application of oil may be 
efficacious for as long a period as four weeks, in the vast majority 
of cases the application will have to be renewed much within that 
time. Where the temperature is high and the surface of the water 
is exposed to the sun, the oil evaporates rather rapidly and has to 
be reneAved at much shorter intervals than where the temperature 
is low and the collection of water is Avell shaded. 

It would seem that the most sensible rule for reneAving the oil 
would be to reoil every two weeks. We know that the average life 
of the larAue of mosquitoes is from 10 to 14 days, and if the oil be 
reapplied at these intervals we will be sure to destroy the A^ast 
majority of the larvae. HoweA^er, if inspection of the oiled water 


PROPHYLAXIS OF MALARIA. 


63 


shows that the oil has in part or wholly disappeared before the end 
of two weeks, it is obvious that reoiling should be done at once. The 
two-week interval was the time adopted by the Army medical officers 
in Cuba and was found to give satisfaction. 

In some regions the use of oil as a larvacide is practically impos¬ 
sible owing to the currents produced by the strong winds of the 
locality or to the development of tropical vegetation in the collec¬ 
tions of water to be oiled, thus preventing the spreading of the oil 
over the water surface. In such instances the use of a larvacide 
that is less easily displaced by winds and that is capable, to some 
extent, of killing vegetation is indicated, but up to the present 
time such an ideal larvacide has not been discovered, the nearest 
approach to it being the one used in the Canal Zone and which will 
now be described: * 

The Canal Zone larvacide .—This preparation has been very largely 
used in the Canal Zone, and all of the reports concerning its action 
are very satisfactory. Darling 23 has described the method of manu¬ 
facture and has conducted valuable experiments determining its 
efficiency when brought in contact with the larvae of both Culex and 
Anopheles mosquitoes. He thus describes the method of preparing 
the larvacide: 

One hundred fifty gallons of crude carbolic acid (specific gravity not greater 
than 0.97 and to contain not less than 30 per cent tar acids) are heated in an 
iron tank having a steam coil with steam at 50 pounds pressure. Two hundred 
pounds of finely crushed and sifted common rosin are dissolved in the heated 
acid, and then 30 pounds of caustic soda, dissolved in 6 gallons of water, are 
added. There is a mechanical stirring rod attached to the tank. The product 
is ready in a few minutes, yielding about 34 barrels. 

Regarding the value of this preparation as a larvacide, he says: 

The resultant emulsion makes a very good disinfectant or larvacide. In fact, 
1 part of it to 10,000 parts of water will kill anopheles larvae in less than half 
an hour, and 1 part to 5.000 parts of water will kill anopheles larvae in from 5 
to 10 minutes or less. This property of killing larvae rapidly is of great im¬ 
portance in ihe Tropics, where continuous rainy periods make crude oil or 
kerosene much less valuable as a larvacide than it is in northern latitudes hav¬ 
ing less rainfall. Also the larvacide acts as an algecide, and thus destroys the 
food and hiding places of anopheles larvae. 

This larvacide is used by spraying an emulsion,. prepared by add¬ 
ing 1 part of the larvacide to 5 parts of water, over the surface 
and along the edges of ponds, streams, or other collections of water 
that serve as breeding places for mosquitoes. 

Used in this 'manner the larvacide will kill all anopheles larvse 
within five, minutes,, and it .possesses the advantage that after a few 
hours, in;case of running streams, the water will be again fit for 
domestic use*.. . 

* This larvacide would appear to be an ideal one for adoption by 
the Army in its antimosquito work, especially in the Tropics where 



64 


PROPHYLAXIS OF MALARIA. 


the use of kerosene is expensive and often inefficient. The cost of 
preparing it is stated by Darling to have been but $0.1413 per gallon, 
which is very much less than any fuel oil can be purchased for. and 
1 gallon of the larvacide makes 6 gallons of the preparation when 
diluted with water for use in the spray. In addition this larvacide 
is a good germicide, having a Rideal-Walker coefficient of from 2 
to 5. One, or at most two, larvacide plants could supply all the larva¬ 
cide needed in the Philippines, and the same is true of the United 
States, and the manufacture and use of this substance bv the Govern¬ 
ment would result in a considerable reduction in the cost of malaria 
prophylaxis and at the same time furnish the Army with a more 
efficient larvacide than kerosene oil. 

Other Icirvacides .—Among other substances that have been recom¬ 
mended as larvacides may be mentioned permanganate of potassium, 
sulphate of copper, corn oil, Phinotas oil, and many proprietary 
preparations. None of these are as efficient as the larvacides already 
mentioned, and the only one that has been used extensively is Phino¬ 
tas oil, which has been used to a considerable extent upon the Isthmus 
of Panama. It is capable of quickly killing the larvae, but also kills 
fish, so that it should not be used where it is desired to preserve the 
latter. 

Although it is possible to secure very excellent results in the 
prophylaxis of malaria by the use of larvacides the method is always 
an admission that we are unable to control mosquito breeding by the 
much better one of abolishing the breeding places of these insects, 
and it should never be adopted in preference to the latter. Under 
the best conditions it is imperfect and the results are not to be com¬ 
pared with those obtained by drainage or filling in of breeding places. 
In addition, especially in the Tropics, the method is more expensive, 
because the results are not permanent, the use of the oil having to 
be continued for months, while, even in temperate regions, it is 
doubtful if this method is as economical as the abolition of the 
breeding places. It finds its greatest field of usefulness in those 
instances where breeding places can not be abolished owing to the 
expense involved, or where open ditches and streams can not other¬ 
wise be prevented from becoming breeding places of these insects. 

Destruction of larvce by fish .—The well-known fact that several 
species of fish are voracious devourers of mosquito larva? has been 
taken advantage of in the prophylaxis of malaria, and there are 
many accounts in the literature of attempts to render the breeding 
places of mosquitos harmless by the introduction of fish that will 
devour the larvae. There is no question that in many instances these 
attempts have met with a considerable amount of success but, as a 
rule, the results have been disappointing. The fish that are the most 
useful are the roach, carp, top minnows, and the goldfish, the roach 


PROPHYLAXIS OF MALARIA. 


65 


and top minnows especially being very active in devouring the larvae. 
W here there are small ponds or artificial collections of water of 
limited extent the stocking of them with these fish will often result 
in keeping them comparatively free from mosquito larvae, but the 
method, at best, is a very imperfect one, and possesses little of value 
for the military sanitarian, although, in very exceptional cases, it 
might yield good results. 

The abolition of breeding places in and about quarters and bar¬ 
racks. —It has already been stated that anopheline mosquitoes will 
breed in even the smallest collections of water and that, with several 
species, it makes no difference what the quality of the water may be. 
The old idea that the Anopheles will only breed in clean water and 
only in streams or larger collections of water has long ago been 
abandoned, and we now know that they will breed both within and 
without quarters and barracks wherever a collection of water forms 
large enough to contain the mosquito eggs. This renders the sani¬ 
tation of quarters and barracks of the very greatest importance in 
any campaign against malaria in a military post, and it is remark¬ 
able how many breeding places may be discovered around and in 
quarters and barracks that are believed to be perfectly free from 
them. Among the breeding places that occur in the quarters and 
barracks may be mentioned uncovered fire buckets, stopped drains, 
the unused hoppers in toilets, unscreened water tanks, earthenware 
vessels containing water, tubs, water traps that are not flushed out 
frequently, and the cans of water that are often used in the Tropics 
to place table legs in to prevent ants from getting to the food. All 
of these are favorite breeding places of certain species of Anopheles 
and are very frequently overlooked by those having little knowledge 
of the habits of these mosquitoes. 

If the post is in the neighborhood of native quarters, as generally 
happens in the Philippines and our other tropical possessions, the 
condition of these quarters as regards the breeding of mosquitoes be¬ 
comes of paramount importance and necessitates the greatest care in 
inspecting and abolishing the numerous breeding places that are 
always present around and in native houses. An inspection of the 
premises will generally reveal larvae in the water that has collected in 
broken bottles, old culinary utensils, tin cans, tin-lined boxes, water 
barrels, and chicken troughs. In addition, puddles of water will 
often be found teeming with larva in the immediate vicinity of the 
dwellings, and even the bamboo fence that surrounds so many native 
houses will be found to breed numberless mosquitoes in the cavities 
left by cutting off the bamboo near a joint or where the mosquitoes 
have gained entrance through holes made by boring insects. 

58000°—14 


5 



66 


PROPHYLAXIS OF MALARIA. 


The discovery of these small breeding places of mosquitoes and 
their proper treatment forms one of the most important duties of 
sanitary officers in localities where malaria is endemic, and the ability 
to make a really scientific mosquito survey of a post and its surround¬ 
ings should be considered one of the most valuable of all possessions 
to one who is engaged in the prevention of this disease. 

All receptacles in which mosquitoes may breed and which are not 
needed in domestic operations should be removed or destroyed, and 
those in which it is necessary to keep water should either be frequently 
emptied, screened, or oiled. Barrels or tubs for the collection of rain 
water, as well as cisterns, should be covered with well-fitted screen 
covers, made of wire containing not less than 18 meshes to the inch. 
Unused hoppers of toilets and water traps should be flushed thor¬ 
oughly at least once a week, and drains should be frequently inspected 
and flushed. One of the most common sources of mosquitoes con¬ 
nected with barracks and quarters are clogged roof gutters, and I 
have frequently found such a gutter alive with larvae after heavy 
rains that had left the gutter full, followed by enough light rain to 
prevent total evaporation of the water. The inspection of all roof 
gutters and their repair, where clogged, is an important prophylactic 
measure in Army posts. 

The fire buckets found in most barracks are prolific sources of 
mosquitoes unless they are properly looked after. All that is neces¬ 
sary in order to prevent the development of larvae is to see that 
they are emptied each week and filled with fresh water. As the 
average life of the larvae is about 14 days, one is perfectly safe if 
the buckets are emptied each week. If desired, wire screen covers 
may be used, but these are expensive and unnecessary if the buckets 
be properly emptied and refilled at weekly intervals. The oiling of 
the water in fire buckets, so frequently observed, is an evidence of 
the lack of knowledge of the life history of mosquitoes on the part 
of the officer ordering such a procedure, and certainly the addition 
of oil to water destined to extinguish fire does not improve its value 
in that direction. The buckets should not be emptied into the sewer, 
but upon the ground in direct sunlight where the water will quickly 
evaporate and the sun kill any larvae that may be present. 

Water troughs for domestic animals should be flushed frequently, 
and in no case should the water be allowed to remain if the trough 
.is not in use. The tanks in water-closets, the sewer traps of the 
post, and open cesspools, if present, should be frequently inspected 
and properly treated, the tanks and sewer traps by flushing or oiling 
and the cesspools by oiling at intervals of two weeks. 

The best way to accomplish the abolition of the small breeding 
places mentioned is to place the work under the charge of a sani¬ 
tary officer, who should be assisted by a good sergeant and the 


PROPHYLAXIS OF MALARIA. 


67 


requisite number of men. If the post is a small one the work can 
be easily accomplished by a sergeant and one or two men, but if the 
area to be covered is large and the buildings are numerous the post 
should be divided into districts, each district being looked after bv 
one man, under the supervision of the sanitary officer and the ser¬ 
geant. Where native barrios or villages have to be sanitated it will 
be necessary, of course, to increase the number of men, but the same 
general plan of organization should be followed. 

Destruction of the adult mosquito .—The adult mosquito may be 
destroyed by various chemicals or they may be caught in mosquito 
traps or by hand. In the military service the methods of destroying 
adult mosquitoes that can be adopted are in general too uncertain 
to be of much value except in fumigating quarters that are to be oc¬ 
cupied by troops in countries where malaria is endemic or upon 
transports plying between malarial and nonmalarial localities. In 
the field the adult mosquito is most easily avoided by methods which 
prevent biting and which are much more practical in application 
than attempts to destroy the insects, although smudges, hereafter 
described, may prove useful in isolated instances. 

A large number of chemicals have been recommended for the de¬ 
struction of adult anophelines, the most important of which will be 
briefly discussed. 

Sulphur dioxide .—Where it is desired to kill the mosquitoes in 
quarters or barracks, in transports or other vessels used for military 
purposes, or in habitations in malarial localities, sulphur dioxide is 
the most valuable agent that we possess. The success attending its 
use in Cuba, Panama, and in Rio cle Janeiro in the fumigation of 
houses, and, indeed, whole blocks of houses, as at Santiago, against 
the yellow-fever mosquito, is familiar to all sanitarians, and the 
same methods used against yellow fever should be employed in the 
case of malaria where the disease is of pernicious type and rapidly 
spreading among troops in quarters. 

In employing this agent it should be remembered that it injures 
most metallic substances and fabrics, and these should be removed 
before fumigation is begun. The methods of fumigation with sul¬ 
phur are well known to all sanitary officers of the Army and will not 
be detailed here. A good rule for determining the amount of sulphur 
necessary to destroy the mosquitoes in fumigation upon a large scale 
is to divide the number of cubic feet in each room of the building by 
500 and reading the result in pounds. Thus, a room 40 feet long. 
20 feet wide, and 12 feet high would contain 9,600 cubic feet, and 
this divided by 500 would give 19.2 pounds of sulphur for such a 

room. 

In the case of malaria it is evident that only in rare instances 
would this method of prophylaxis be used in the military service, 


68 


PROPHYLAXIS OF MALARIA. 


owing to the fact that other and more easily applied methods would 
render it unnecessary. However, there is no doubt of its great value 
in the prevention of the transmission of yellow fever and in great 
epidemics of malaria, such as have occurred among troops in 
quarters, it would undoubtedly be of equal value. 

Smudges. —In the field many adult mosquitoes could be destroyed 
by fires made of material producing a dense smoke, as green vegeta¬ 
tion or bark. The American Indian used this method of rendering 
his tent inhabitable and all hunters are familiar with this device, 
which might prove very useful to an army in the field in regions 
where mosquitoes were very numerous and mosquito nets unob¬ 
tainable. 

Pyrethrum powder. —Pyrethrum powder is made from the dried 
flower heads of plants belonging to the genus Chrysanthemum , grow¬ 
ing in Transcaucasia. The powder is more commonly known as 
Persian or Dalmatian insect powder, and depends for its efficiency 
on the presence of certain oleoresins in the dried flowers, so that to 
be efficient the powder must be comparatively fresh. The best prep¬ 
aration for use in this country is made in California and is marketed 
under the proprietary name of “ buhach ” powder. 

For the purpose of destroying mosquitoes the powder is burned in 
a room, being placed upon a dish or tin and a match touched to it, 
when it will burn slowly and give off a large volume of smoke hav¬ 
ing a peculiar odor; or the powder may be procured in the form of 
cones or pastilles and these burned. The smoke is not harmful or 
very unpleasant to most people, and if the powder be burned in a 
closed room it will stupify all mosquitoes in the room and they may 
be swept from the floor and destroyed. The use of this powder in 
the rooms of quarters infested with mosquitoes might be of benefit 
where other measures could not be taken to get rid of them, but from 
a military standpoint this method of destroying mosquitoes possesses 
little value. 

Numerous other fumigants have been recommended for destroying 
adult mosquitoes, as camphor phenol or Mimm’s Culicide, Pyrofume, 
mercuric chloride, powdered stramonium, and formaldehyde gas, 
but none of them are of any importance in the prophylaxis of ma¬ 
laria in the military service and will not be discussed. 

Mosquito catching as a prophylactic method. —The catching of 
adult mosquitoes, first advocated by Orenstein, 30 in the Canal Zone, 
is really deserving of much greater consideration as a prophylactic 
method than it has received. It is a method that could readily be 
adopted in the military service and, under certain conditions, would 
be a most valuable one, especially in temporary camps in the Tropics. 
In his paper, published in 1918, Orenstein states that this method 
has been extensively employed in the Panama Canal Zone and that 


PROPHYLAXIS OF MALARIA* 


69 


it has given very excellent results. He quotes two instances given 
by Le Prince, which are so striking that I will give them in his own 
words. He says: 

The first systematic application of mosquito catching within habitations as 
a prophylactic measure against malaria, in so far as I have been able to learn, 
was made in the Canal Zone, in April, 1908, at a camp near Cocoli. The camp, 
composed of unscreened tents, was to be maintained only about five months, 
and it was not thought practicable to incur the great expenditure involved in 
a thorough antimalarial campaign. When the camp was first established, as 
many as 30 anophelines could be seen in a tent in the daytime, and many 
more after dark. One man -was employed to kill the mosquitoes in these 
tents. He worked from 0 to 11 in the morning and from 1 to 5 in the after¬ 
noon. In the four and a half months of this camp’s existence the malaria 
incidence was a little over 1 per cent per week. 

Another remarkable instance is described by Le Prince in Ross’s “ The Pre¬ 
vention of Malaria.” In June, 1908, several hundred United States marines 
were quartered for about eight weeks on a hill near Panama, known as Diablo 
Hill. During this period the malaria incidence among the marines was 14 per 
cent per week. In May, 1909, some living cars were located on the same hill. 
The anopheline breeding was just as it has been at the time the marines camped 
there. From the first week in May to the end of November, in the rainy sea¬ 
son. when malaria incidence is high in Panama, only four cases of malaria 
occurred among the 40 laborers occupying these cars, a weekly incidence of 
about 0.3 per cent. The difference was due to having a man devote half an hour 
a day to the destruction of the anophelines found in these cars at a cost of 
5 cents a day for the labor.” 

The above illustrations demonstrate that mosquito catching is 
capable of keeping the malaria incidence down to a very low figure 
even in hotbeds of the disease, and indicates how valuable a method 
this would be in the military service, where it could so easily be 
adopted. 

The mosquitoes are caught with the chloroform tube already de¬ 
scribed in Chapter II, although Orenstein recommends that instead 
of cotton at the bottom of the tube to receive the chloroform a 
layer of short lengths of rubber bands covered with a plug of cotton 
be placed at the bottom of the tube and saturated with chloroform. 
In addition to the killing tube the mosquito hunter is also furnished 
with an ordinary u flv swatter” and instructed to catch or “swat” 
every mosquito observed. The method of catching mosquitoes with 
the tube has already been described (Chapter II, p. —), and the mos¬ 
quitoes should be searched for in dark corners of rooms, in closets, 
along baseboards, beneath sinks and toilet fixtures, behind pictures, 
and in tents, along the ridgepole, in the corners behind clothing, and 
beneath cots and mosquito nets. The “ fly swatter ” is especially use¬ 
ful in killing the mosquitoes frequently observed on the outside and 
inside of screenings on verandas, doors, and windows. At Camp 
Stotsenberg, during the rainy reason, the outside of the window 
screens of the hospital and other buildings was frequently the resting 


70 


PROPHYLAXIS OF MALARIA. 


place of scores and even hundreds of anophelines which were en¬ 
deavoring to get within the buildings, and it was possible to kill 
hundreds of these insects in this situation almost every evening during 
the rainy season. 

Mosquito traps have also been used extensively in the Canal Zone, 
and Orenstein describes one devised by Sanitary Inspector Bath, 
which has proved satisfactory. It consists of a half-cylinder con¬ 
structed of wire netting, having two ridges inside it, “ the apices of 
which are perforated by longitudinal slits about J inch wide and 3 
inches long. Through the slits in these ridges the mosquitoes enter 
the chamber of the trap, and can not, for some reason, find their way 
out again.” 

The traps are so placed as to catch the mosquitoes either when en¬ 
tering or leaving a building, and in the Canal Zone it was found that 
more anophelines were caught if the traps were placed on the lee of 
buildings, while more culicines were captured if the traps were in¬ 
stalled on the windward side of the buildings. 

Regarding the value of catching mosquitoes Orenstein well says 
that: 

When it is remembered that in malaria a period of at least a week must 
elapse before the mosquito which has fed on an infected person can transmit 
the infection to another person, and when it is recalled that an anopheline 
filled with blood becomes sluggish and does not fly very far for some time, the 
efficacy of killing mosquitoes within habitations becomes self-evident. 

And he concludes that u catching mosquitoes by hand within dwell¬ 
ings is a measure of great value in the prophylaxis of malaria. It is 
especially applicable to temporary camps.” 

It is obvious that this prophylactic method might be of the very 
greatest value to the military service in the case of camps in malarial 
localities and it could be so easily put in operation that its neglect 
would be inexcusable. All that would be necessary would be to detail 
a certain number of men for the purpose, under an intelligent non¬ 
commissioned officer, the camp being districted for the purpose. No 
great amount of training is necessary, as mosquitoes are easily recog¬ 
nized and the method of handling the killing tube and u swatter ” is 
quickly acquired even by the most unintelligent laborer, as shown 
by the fact that all the work in this line in the Canal Zone was done 
by the West Indian negro. In the field where troops are in tents 
for some time, as at maneuvers or in more or less permanent camps, 
and where mosquitoes are prevalent, this method is certainly deserv¬ 
ing of the most thorough trial. 

In barracks and quarters in posts situated in the Tropics mosquito 
catching would also be a valuable method of prophylaxis and could 
be accomplished by native help at a comparatively small expense. 
In many posts in the Philippines, where it has been found impossible 


PROPHYLAXIS OP MALARIA. 


71 


to entirely eradicate mosquitoes, this method would be easy of appli¬ 
cation and would undoubtedly give good results in reducing the 
number of mosquitoes and the incidence of malaria. In temperate 
regions it is generally possible to rid our posts of mosquitoes by one 
or more of the other methods described in this chapter, but in the 
Tropics it is very often impossible to do more than reduce the num¬ 
ber of these insects, and this would appear to be a great aid in that 
direction, and possesses the additional value that it enables us to 
capture and kill the mosquitoes that have bitten man and may, there¬ 
fore, have become infected with malaria. 


Chapter IV. 


PROPHYLACTIC METHODS BASED UPON THE PROTECTION OF MAN 

FROM THE BITES OF MOSQUITOES. 

Where it is impossible to destroy all of the breeding places of 
mosquitoes or to kill the adult insects, the protection of man from 
the bites of these insects becomes a most important prophylactic 
measure. Especially has this been found true in the military service, 
where this method, together with quinine prophylaxis, often has to 
be depended upon entirely when troops are in the field in malarial 
localities, and even in semipermanent camps and permanent posts 
the protection of the troops from the bites of mosquitoes not infre¬ 
quently becomes of paramount importance owing to local conditions 
or for economical reasons. While, as has been stated, the abolition 
of the breeding places of mosquitoes is the ideal method of malaria 
prophylaxis either in military or civil communities and other meth¬ 
ods should never be substituted for this where it is possible to employ 
it, the fact remains that in most localities it is necessary to combine 
all of our methods of prophylaxis, and of them the protection of man 
from mosquito bites is one of the most valuable. 

This mechanical prophylaxis, as it is sometimes called, is secured 
by the proper screening of quarters and barracks, the use of mosquito 
nets for the beds and shelter tents, the wearing of head nets and 
gloves, and the use of various odorous substances which are smeared 
upon the skin for the purpose of preventing mosquitoes from biting. 

Screening .—The screening of barracks and quarters in posts in 
malarial regions is a most important and valuable prophylactic meas¬ 
ure and should never be neglected when the more permanent methods 
of drainage and filling in can not be employed or where their em¬ 
ployment only reduces the number of anophelines. While, in civil 
iife, the question of expense makes the employment of this method 
prohibitive in many localities, in the military service it should not 
enter into the question where posts are situated in regions where 
pernicious forms of malaria are prevalent, or where any form of 
malaria is prevalent to an extent that will seriously affect the 
efficiency of troops. 

The expense involved is admittedly great, in many instances, but 
if good screening material be obtained, the screens will, if properly 
cared for, last for years, and before they are worn out will have 
repaid many times the initial expense by the reduction in the amount 
of malaria among the troops and the consequent increase in efficiency. 


72 


PROPHYLAXIS OP MALARIA. 


IS 


The selection of screening material. —The screening used for 
quarters and barracks should be of as durable material as it is 
possible to secure and of fine enough mesh to keep out all anophelines. 
The material for screening should be of wire composed of copper, 
zinc, and iron, the copper content being higher than that of brass. 
In the Tropics this is of special importance, as the heat and moisture 
rapidly corrode wire netting having a low percentage of copper. 
The observations of Nauss, in the Canal Zone, reported by Darling, 31 
proved that the deterioration of wire screening in the Tropics is due 
to the presence of iron plus the influence of a hot and moist climate. 
Brass screens, by reason of the amount of iron alloy present are, 
therefore, unsuitable, and copper-wire screens should always be 
selected. 

If copper screening can not be obtained ordinary iron-wire screens 
may be used, but they should be covered with two coats of good paint 
and frequently repainted. Even so, they will be found more ex¬ 
pensive in the end than the best copper-wire screening, which should 
be used if it can be obtained. 

The size of the mesh in the wire screening used to protect houses 
and barracks is a matter of prime importance. It must be close 
enough to keep out all anopheles mosquitoes, and in regions where 
yellow fever is endemic or may be introduced the mesh should be 
small enough to keep out the yellow-fever mosquito, Stegomyia fas- 
ciata. Nothing is gained by using a screen in which the meshes are 
closer than necessary, and something is lost, for the closer the mesh 
the more air is excluded from the room or building, and this is a 
matter of much importance, especially in the Tropics and subtropics. 

A considerable amount of experimental work has been done along 
this line. As a result of my own observations at Camp Stotsenburg, 
in the Philippines, where anophelines were very numerous, I con¬ 
cluded that wire netting containing 16 meshes to the linear inch 
(No. 16, as it is called) excluded all the Anopheles tested and that 
this size netting should be used in the prophylaxis of malaria. 32 My 
observations were confirmed, so far as Anopheles are concerned, by 
Guiteras, 33 Darling, 34 and the United States Army Board 35 for the 
Study of Tropical Diseases in the Philippines. This netting was not 
efficient, however, in excluding the yellow-fever mosquito, as the 
majority of investigators have shown, and a netting containing 18 
meshes to the linear inch should be selected when Stegomyia are 
present, as shown by the experiments of Darling and the Board for 
the Study of Tropical Diseases. 

It is very probable that mosquitoes vary in size, even when full 
grown, for Goeldi has shown that delayed development during the 
larval stage, due to various local conditions and a poor supply of 
food, results in dwarfed adult mosquitoes, and this doubtless accounts 


1 4 


PROPHYLAXIS OF MALARIA. 


for some of the discrepancies between the results of different in¬ 
vestigators as to the efficiency of various sized wire screens. 

In 1908 Col. J. It. Kean, Medical Corps, United States Army, sent 
Dr. Guiteras, in Habana, some 16-mesh wire screening and requested 
that experiments be made regarding its efficiency in excluding ste¬ 
gomyia mosquitoes. After many very careful experiments Dr. Gui¬ 
teras reported to Col. Kean that the netting sent kept out Stegomyia 
fasciata , using the following words: 

It is my opinion that we may conclude from these experiments that the Ste- 
iiomyia calopus ( fasciata ) can not pass through the wire gauze sent for trial. 
The gauze is 16-wire mesh—that is, it presents 16 wires or threads to the linear 
inch. 

In 1910 Darling, as the result of his experiments in the Canal Zone, 
states: 

In regions where it is only necessary or desirable to protect against anophe- 
lines a No. 16 mesh screening (16 holes to the inch) would answer the purpose, 
and where, as in this region, it is necessary to protect against some of the 
smaller varieties, such as Stegomyia calopus , a No. 16 mesh would be practically 
safe, but not absolutely so. 

He found that none of the anophelines in the Canal Zone could 
pass the 16-mesh screening, but that some specimens of Stegomyia 
fasciata (calopus ) could, as well as several species of Culex. 

Owing to the uncertainty caused by the divergent reports of 
Guiteras and Darling, the Surgeon General of the Army, in 1912, 
requested the Army Board for the Study of Tropical Diseases in the 
Philippine Islands to determine what sized copper-wire gauze would 
prevent the passage of anophelines and other mosquitoes. The 
board, as the result of very careful experiments, found that 16-mesh 
wire gauze was impervious to the following mosquitoes: Myzomyia 
rossii , Mizorhynchus barbirostris , Pyretophorus freerae , Mansonia 
annulifera, Mansonia uniformis , Culex fatigans , and Culex microan- 
nulatus. As Myzomyia rossii is as small as any of the anophelines 
connected with malaria, their observations confirm mine, made in 
1905 at Camp Stotsenburg, but they also determined that this same 
species could be excluded by either No. 12, 14, or 16 mesh screening. 
In addition they found that Stegomyia fasciata (calopus) could pass 
No. 16 mesh netting with considerable ease, and concluded that while 
the No. 16 mesh will keep out all malaria mosquitoes found in the 
Philippines its use is inadvisable because it does not keep out the 
yellow-fever mosquito. 

From these various observations it appears to me that in the mili¬ 
tary service all screening should contain at least 18 meshes to the 
linear inch, and I believe that it is a mistake to use wire gauze con¬ 
taining more than this number, both because it is unnecessary so far 
as practical protection goes and because it reduces by just so much 
the amount of air admitted to a room or building. 


PROPHYLAXIS OF MALARIA. 


75 


Method of screening .—It is a perfectly obvious fact to anyone who 
inspects screened buildings, either in civil or military life, that much 
of the screening is so constructed as to defeat, in a measure, the pur¬ 
pose aimed at, i. e., the exclusion of mosquitoes. The use of adjust¬ 
able or folding screens; the fastening of the screen within the win¬ 
dow, necessitating its being raised every time the window is opened; 
and the use of the single-screened door for quarters and barracks, in¬ 
stead of having double-screened doors with a screened vestibule, are 
all instances commonly observed of imperfect screening. In bar¬ 
racks that Avere caiefullv screened I haA r e observed unscreened venti- 
lators along the ridgepole, which explained fully the presence of 
numerous mosquitoes within them, an occurrence which had fur¬ 
nished a strong argument against screening in the prophylaxis of 
malaria to certain individuals avIio Avere adA T erse to this method. Not 
infrequently, Avhile the first and second stories of quarters are care¬ 
fully screened, the attic windows will be found unscreened, and 
mosquitoes thus gain entrance to the quarters. All of these mistakes 
can be easily avoided and are most important in their effect upon the 
success of screening against mosquitoes. 

The arrangement of screens must vary, of course, Avith the archi¬ 
tecture of the building to be screened, but all window screens should 
be placed outside window sashes and fitted as closely as possible to 
the sash, as otherwise mosquitoes may easily get in between the screen 
and sash, especially when the window is partly open. In fact, to 
insure perfect protection the entire window should be coA^ered exter¬ 
nally by one screen. In this way either the lower or upper sash may 
be raised or lowered without danger of admitting mosquitoes. 
Where wire screening is impossible doors and windows may be pro¬ 
tected by cheese-cloth screens, which, Avhile not very durable, are sat¬ 
isfactory if carefully watched for the appearance of holes and 
promptly replaced. All entrances to quarters and barracks where 
screening is necessary should be protected by a screened vestibule 
containing tAvo doors instead of a single screened door opening di¬ 
rectly into the building, which is the usual arrangement. While this 
method of screening may be practically sufficient Avhere mosquitoes 
are not very numerous and malaria is rare, it is necessary to have the 
double-door entrance in regions where malaria prevails to anv extent, 
especially in barracks, where the doors are opened so frequently. 
All screened doors should open outward. 

Extreme care should be taken that all ventilators be screened, and 
that screens be frequently inspected and repaired promptly when 
necessary. 

Mosquito nets or bars .—When it is impossible to thoroughly screen 
barracks and quarters, and for troops in the field, the mosquito net 
or mosquito bar, as it is often called, furnishes a most valuable means 


76 


PROPHYLAXIS OF MALARIA. 


of protection from the bites of these insects. In the military service 
the ideal mosquito net would be one that could be used over the bed 
while the troops are in permanent barracks, and within the shelter 
tent when in the field. Such a mosquito net has been devised by Capt 
Yedder, of the United States Army Medical Corps, and has been 
adopted by the Quartermaster’s Department for issue to the troops. 
It can be easily folded and carried in the pack when troops are in the 
field and, if properly made., will undoubtedly be found to be a most 
valuable aid in preventing mosquito-borne diseases in an army during 
active operations, besides greatly increasing the comfort of the troops 
when campaigning in regions where mosquitoes abound. 

In barracks where mosquito nets are used there should be a nightly 
inspection of the nets after taps, to insure their being used by every 
man and that they are being properly used. Care should be taken 
to see that each net is tucked under the mattress, instead of hanging 
loosely around the bed, as otherwise mosquitoes easily gain entrance 
by crawling or flying between the net and the mattress. During the 
day the mosquito net should be preferably taken down and folded 
up on the bed, but may be either tucked in beneath the mattress if 
the bed is made up or folded over on the portion suspended between 
the uprights. The greatest care should be taken to keep the net in 
repair, all holes being darned as soon as they are discovered. 

Head nets and gloves .—Head nets and gloves are absolutely neces¬ 
sary in many regions if one is camping or hunting, and the same is 
true when troops are in the field in such localities. The Quarter¬ 
master’s Department of the Army issues a very good head net, so 
fashioned as to fit over the campaign hat, and this will be found of 
the greatest service, especially to the men on guard, and their use 
should be insisted upon in malarial localities. I am convinced that 
if a head net had been worn by men on guard at several of the posts 
in the Philippines it would have greatly reduced the amount of 
malaria, for many cases of infection occurred that could be traced 
to the soldiers being severely bitten during guard duty. 

The use of odorous substances on the skin .—Various substances 
have been recommended for protecting the skin from the bites of 
mosquitoes. Among the best may be mentioned the oils of citronella, 
eucalyptus, pennyroyal, anise, camphor, vaseline, and kerosene. 
As a rule the slight protection afforded by these substances has not 
led to any extensive use of them in the military service, but there may 
be circumstances in which the use of one or the other of them may 
prove of value. Such an instance is quoted by Howard, 36 who states 
that Dr. AY. H. Dade, United States Army, found a mixture of one 
part of bergamot oil to sixteen parts of kerosene very efficacious in 
preventing mosquito bites when smeared on the skin, and that this 


PROPHYLAXIS OF MALARIA. 


77 


mixture was successfully used by troops when on marches in the 
Philippines. 

For use, as a temporary measure, a mixture of oil of citronella 
and vaseline, when smeared upon the skin, is very serviceable and 
is not unpleasant. If liquid vaseline is used, about one part of oil 
of citronella should be mixed with six parts of liquid vaseline and 
applied frequently when exposed to the bites of mosquitoes. If 
liquid vaseline can not be obtained ordinary vaseline may be used, 
a teaspoonful of the oil of citronella being mixed with two ounces of 


vaseline. 

It is obvious that the use of substances that are only temporary 
in their protective power and that depend entirely upon the will of 
the individual for what success they may have, are not of any great 
value in the prophylaxis of malaria in the military service. Such 
methods are miserable makeshifts and should be rendered unneces¬ 
sary by the adoption of more scientific and valuable ones. 

The value of screening and the use of the mosquito net has been 
abundantly proven by practical experiments, beginning with that of 
Sambon and Low. These investigators, in order to test the truth of 
the theory that the malarial infections are transmitted by mosquitoes, 
spent an entire summer at Ostia, a most malarious region in the 
koman Campagna, residing in a mosquito-proof hut. During the 
day the time was spent mostly out of doors, but early in the after¬ 
noon the observers retired to their hut and there spent the night. 
Neither investigator developed malaria, although it was said, by the 
natives, that to spend one night in that place would result in a 
malarial paroxysm, and most of the inhabitants who were not pro¬ 
tected by screens developed the disease during the summer the ob¬ 
servers spent there. 

Of the notable instances of the protection from malaria afforded 
by screening may be mentioned the experiments of Procaccini, in 
Sardinia, and of Tzuzuki, in Formosa, with military troops; and in 
the Canal Zone, in the settlements of Gatun and New Gatun, as re¬ 
ported by Orenstein. 

Procaccini, 37 in Sardinia, reduced the number of cases of malaria 
among the soldiers from 70 per cent to 57 per cent, in one season, 
by screening the barracks, and later the percentage was reduced to 
less than 20 per cent. 

In Formosa, Tzuzuki 3S tested the efficiency of screening by select¬ 
ing 115 soldiers of a battalion stationed at Kirun, a most malarious 
locality, and furnishing them with screened barracks, the remainder 
of the battalion being unprotected from the bites of the mosquitoes. 
The 115 soldiers were thus protected from September 21 to De¬ 
cember 8. the malarial season, and not a case of the disease developed 
among them, while, in the same time, among the 750 soldiers not so 


78 


PROPHYLAXIS OF MALARIA. 


protected there developed 319 cases of malaria. The men were con¬ 
fined in the screened barrack from half an hour before sunset to 
half an hour after sunrise during this time, and wore head-nets 
and gloves when on service at night. 

Orenstein 39 gives a most interesting account of the value of screen¬ 
ing as illustrated in the settlements of Gatun and New Gatun, in 
the Canal Zone. Gatun had a population of approximately 4,500, 
residing in screened quarters, while New Gatun, having a popula¬ 
tion of about 5,000, had no screened quarters. With this exception 
the surroundings were identical so far as chances for malarial infec¬ 
tion were concerned. Observation extending over three years showed 
that the malarial incidence for Gatun and New Gatun was as 2 is 
to 3, the following being the yearly incidence in each settlement: 


Year. 

Gatun. 

New 

Gatun. 

1909. 

Per cent. 
5.35 
5.37 
8.75 

Per cent. 
10.04 
9.21 
12.59 

1910. 

1911. 



In his conclusions Orenstein says: 

A properly screened dwelling can be depended upon to reduce by at least one- 
third the malaria incidence in a locality where malaria is endemic. 

These instances illustrate how valuable a prophylactic method we 
possess in screening when it is efficiently applied, but it should be 
remembered that it is far less valuable than is the abolition of the 
breeding places of mosquitoes when this can be accomplished. How¬ 
ever, as has been repeatedly stated, it is only under exceptional con¬ 
ditions that one is able to entirely rid a locality of mosquitoes, and 
it therefore follows that screening must always remain one of our 
most valuable accessory methods in the prophylaxis of these infec¬ 
tions. In the field, of course, we must depend entirely upon the 
use of the mosquito net and quinine in the prophylaxis of malaria 
among troops, but in permanent posts screening should not be de¬ 
pended upon to the exclusion of other prophylactic measures, but 
should be used along with them. 

Screening of malarial patients .—In concluding this chapter I de¬ 
sire to call attention to the very great importance of screening all 
malarial patients as long as the plasmodia can be demonstrated in 
any number in the peripheral blood. It is obvious that if we place 
the infected individual in a position where mosquitoes can bite him 
the mosquitoes will become infected, provided gametes are present, 
or the patient may become reinfected by the bite of an infected mos¬ 
quito. Despite these facts I have several times observed malarial 
patients in a common ward lying unprotected by a mosquito net, 














PROPHYLAXIS OF MALARIA. 


79 


although the ward was not screened and anophelines were present. 
It is needless to comment upon such a situation, but it is one 
that will continue to occur, in isolated instances, until the malarial 
fevers are considered as infectious diseases and the same precautions 
taken to prevent their spread as would be taken in the case of yellow 
fever. 

In a carefully screened ward it would be unnecessary, of course, 
to further screen a malarial patient, but in an unscreened ward this 
should always be done, and, under such circumstances, it is better to 
place the patient in a room by himself, the same precautions being 
taken regarding screening, nor should he be allowed to leave the 
screened quarters until the plasmodia have either disappeared from 
his blood or been reduced to a noninfectious minimum. This will, 
of course, necessitate a microscopic examination of the patient's blood 
at daily intervals, but it is only by such an examination that we can 
adequately control the treatment of malaria and render the pro¬ 
phylaxis of the disease effective, so far as the patient is concerned. 
The screening of every individual in hospital for malarial fever is 
an absolutely necessary prophylactic measure if one desires to limit 
the spread of these infections. 


Chapter V. 


PROPHYLACTIC METHODS BASED UPON THE DESTRUCTION OE 
MALARIA PLASMODIA (QUININE PROPHYLAXIS). 

It is obvious that if we can destroy or prevent the development of 
the malaria plasmodia in infected individuals we will succeed in 
preventing the disease, as it will thus be impossible for mosquitoes 
to become infected. This fact is the basis of quinine prophylaxis, 
which consists in the administration of this drug to all individuals 
harboring the plasmodia and to all those exposed to the bites of 
mosquitoes capable of transmitting the plasmodia to man. 

Perhaps no method in the prophylaxis of the malarial feA r ers has 
given rise to more controversy than the use of quinine as a prophy¬ 
lactic. Enthusiasts in its favor have claimed that the use of this 
drug alone is all that is needed to eradicate malarial infections from 
any locality, while its most violent enemies have claimed that it is 
not only practically useless but even harmful. It is evident that 
the truth must lie somewhere between these extreme opinions, and 
it is my belief that quinine prophylaxis is a most valuable method, 
but one that should not be relied upon to the exclusion of other 
methods except under conditions that render the combination with 
other methods impossible. 

From the observations of many investigators we know that quinine 
is capable of destroying the plasmodia while they are in the blood 
of man, and from clinical observation we know that this destruction 
is followed by the disappearance of the symptoms of infection 
and the recovery of the patient. In other words, quinine is a specific 
in the treatment of malaria, and to deny the efficacy of the same 
drug, when properly administered, in the prophylaxis of the same 
disease is absurd. If quinine can destroy the plasmodia after symp¬ 
toms of infection are present, it will certainly destroy them before 
they become numerous enough to cause symptoms; but experience 
has shown that enough of the drug must be given to really destroy 
the parasites, and that this means that considerable doses have to be 
taken and have to be continued just as long as the individual is ex¬ 
posed to malaria mosquitoes. 

The most ardent advocates of this method of prophylaxis, as Koch, 
have claimed that by it alone it is possible to rid a community of 

80 


PROPHYLAXIS OF MALARIA. 


81 


malaria, blit in practice this result could only be attained where the 
drug could be administered to every individual in the infected locality 
for a long period of time, for the prophylactic use of the drug would 
have to be continued as long as Anopheles were present, for just so 
long would there be danger of the spread of the disease from the 
mosquitoes becoming infected by imported cases of malaria. There¬ 
fore it follows that while quinine prophylaxis is a method of the 
very greatest value in the prevention of malaria, it can not be de¬ 
pended upon alone, but should be combined with those that have 
already been described. 

The results achieved by this method of prophylaxis have varied 
greatly in different localities, depending upon the methods of admin¬ 
istration and the form of quinine used; the efficiency with which the 
administration of the drug has been conducted; and the class of 
people with whom the method has been tried; so that the literature 
is filled with discordant reports regarding the value of the drug 
as a prophylactic. Most of the unfavorable reports have been the 
result of careless application of the method or of lack of control of 
the people to be benefited. It is obvious that to be successful the 
drug must be regularly administered, and in the military service 
this can be done, whereas it might be impossible in civil commu¬ 
nities. It is true, however, that even when the method has been 
given the most careful trial it has failed, in rare instances, to have 
much effect upon the incidence of malaria; but the experience of 
numberless observers of the great value of the method when properly 
applied leaves no doubt of its worth, and the rare failures recorded 
must have been due to exceptional conditions surrounding the experi¬ 
ments. 

Among the arguments that have been urged against quinine pro¬ 
phylaxis may be mentioned the production of haemoglobinuria, 
harmful physical effect upon the consumer, the difficulty of applica¬ 
tion, and the danger of producing a resistant strain of the plasmodia 
by the exhibition of small doses of quinine over long periods of 
time. As a matter of fact none of these objections are valid, and 
there is practically no proof that any of them possess actual merit 
sufficient to forbid the use of quinine in this manner. Haemoglobi¬ 
nuria is sometimes produced by quinine, but very rarely where the 
drug is taken regularly, and the few instances in which it does occur 
is no argument against the use of the drug. There is absolutely no 
scientific proof that the taking of quinine, even in much larger doses 
than are used in prophylaxis and continued for weeks and months, 
produces any harmful effect, and even the slight dizziness and roar¬ 
ing in the ears disappear after taking the drug in prophylactic doses 
for a few days. The danger of producing quinine-fast strains of the 

58000°—14-6 



82 


PROPHYLAXIS OF MALARIA. 


plasmodia in this manner is simply a theory without any proof of 
scientific value, while the objection regarding the difficulty of apply¬ 
ing the method is true of many other prophylactic methods and a 
poor excuse for its neglect. Certainly in the military service, where 
men are under absolute control, there can be no excuse for neglecting 
quinine prophylaxis when it is needed, because it requires careful 
supervision and therefore entails labor upon the sanitary personel. 
Quinine prophylaxis has been found of the greatest service in keep¬ 
ing down the incidence of malaria in some of our permanent posts 
in the Philippines, and during active operations by troops in the 
field in malarial regions it will always have to be our chief defense 
against these infections. It is therefore essential that the medical 
officer be acquainted with the various methods of applying this form 
of prophylaxis, which includes a knowledge of the effect of quinine 
upon the plasmodia; the form and time of administration of the 
drug; the proper treatment of initial infections, of latent infections, 
and of gamete carriers; and, finally, of the results that may be ex¬ 
pected from this method when it is efficiently applied. 

Action of quinine upon the malarial plasmodia. —In 1807 Binz 
demonstrated that quinine in solution killed infusoria with which 
the solutions were brought in contact, and concluded from this that 
its effect in malaria was due to the destruction of the cause of the 
disease. In 1881 Laveran demonstrated that quinine solutions, when 
added to blood containing the plasmodia, produced immediate cessa¬ 
tion of the movements of the plasmodia, while Golgi, Romanowsky, 
Mannaberg, Zieman, Sehaudinn, and others described degenerative 
changes produced by the drug in the various species of plasmodia. 
The results of these various observers were often conflicting, and 
many of their conclusions were founded upon insufficient evidence. 
In 1910 1 40 published the results of continued studies upon the effect 
of quinine on the various species of plasmodia, as shown in both fresh 
and stained preparations of blood, and these results have since been 
confirmed by many obser\ r ers. They may be summarized as follows: 

Plasmodium vivax (tertian plasmodium ).—In fresh preparations 
of blood obtained after the administration of quinine marked mor¬ 
phological changes are observed in every stage of development, with 
the exception of the stage just preceding sporulation and in the 
fully-developed gametes. The morphological changes observed in 
the living organism consist in an initial stimulation of amoeboid 
activity, followed by a decrease in activity, and eventually by cessa¬ 
tion of all motion; a granular degeneration of the cytoplasm which 
has an increased refractive index; fragmentation of the plasmodium, 
followed by the apparent extrusion of the fragmented organism from 
the red corpuscle; and an apparent increase in the amount of pig¬ 
ment in those organisms which undergo development in spite of the 


PROPHYLAXIS OF MALARIA. 


83 


quinine. In stained preparations the morphological changes are 
much more apparent, consisting in poor staining reactions of the 
cytoplasm, while the chromatin of the nucleus stains darker and is 
stainable long after the cytoplasm has ceased to stain; the preven¬ 
tion of normal increase in the amount of chromatin, as shown by the 
plasmodia containing much less of this material at certain stages of 
growth than normal; the prevention of normal division, as shown by 
plasmodia in which only a portion has divided, thus producing 
atypical sporulating forms; and sporulating forms in which many 
of the spores or merozoites are devoid of chromatin. Many of the 
organisms show undoubted evidences of fragmentation in the stained 
preparations. The changes observed are present at every stage in 
the development of the organism except when quinine has been given 
just before sporulation and in the fully-developed gametes. 

Plasmodium malariae (quartan plasmodium ).—The changes pro¬ 
duced by quinine, as shown in fresh and stained preparations of 
blood containing Plasmodium malariae , are essentially the same as 
those produced in Plasmodium vivax , and while there is some 
evidence that this species is slightly more resistant that the tertian 
plasmodium my observations showed that even the older parasites 
were affected, just as in the case of the tertian species. 

The estivo-autumnal plasmodia. —In both species of estivo- 
autumnal plasmodia quinine produces practically the same changes 
as in the tertian and quartan species, except that fragmentation is 
not so frequently observed. The crescentic gametes of the estivo- 
autumnal plasmodia appeared unaffected by quinine so far as any 
morphological changes are concerned. 

My observations proved that the old theory that only the young 
spores are affected by quinine and that the drug must be in the 
blood at the time of sporulation is untenable, for while the merozoites 
are undoubtedly more easily affected by the drug than the older 
forms, the changes in morphology of the schizonts almost up to the 
time of sporulation demonstrate conclusively that quinine causes 
degeneration in even the older plasmodia. Recent observers have 
confirmed my observations regarding the action of quinine upon the 
later stages in the development of the plasmodia and upon the mor¬ 
phological changes that are produced in these organisms by the drug. 
Rieux 41 studied the action of the drug upon the tertian plasmodium 
and found that not only were the young schizonts affected, but that 
if the drug was commenced 24 hours after the paroxysm when the 
schizonts were half grown many of them Avere arrested in develop- 
ment and fragmentation occurred in a considerable percentage. He 
found that the sporulating bodies were not affected, but that the con¬ 
tinued use of quinine caused degeneration of the gametes and eventu¬ 
ally a disappearance of these forms from the peripheral blood. Bil- 


84 


PROPHYLAXIS OF MALARIA. 


let's 42 observations confirmed those of Rieux; and James 43 , in the 
Canal Zone, obtained the same results from his studies of the action 
of quinine upon the plasmodia. 

From these observations it is evident that quinine is capable of 
affecting the plasmodia in practically every stage of their develop¬ 
ment, and it follows that the best results will be obtained in prophy¬ 
laxis and treatment if the drug is present in the blood continually. 
Thus, I am a firm believer in divided doses at regular intervals in 
the treatment of all forms of malarial infections, except, of course, 
the pernicious cases, where a large dose of the drug must be admin¬ 
istered at once; and in the prophylaxis of the disease I believe that 
better results will be obtained if quinine be given in morning and 
evening doses rather than in one dose during the 24 hours. The 
object desired is to have a maximum quantity of the drug continually 
present in the blood, and the nearer we approach this ideal the better 
will be our results with the quinine prophylaxis of malaria. In 
the field, of course, it would probably be necessary to depend upon 
one dose, given either in the morning or evening, but in camps and 
posts a morning and evening administration of quinine could be 
arranged and enforced in the vast majority of instances. 

The form, of quinine to he used in prophylaxis .—Until quite re¬ 
cently we have been very ignorant regarding the exact fate of 
quinine after ingestion and the salts or compounds of the drug best 
fitted for use in the prophylaxis and treatment of malaria. The 
researches of Gaglio, MacGilchrist, Webb, and others have demon¬ 
strated that many of our ideas regarding the pharmacology of this 
drug were erroneous and have resulted in new points of view as to 
its use in malarial infections. Thus, the old idea that the salts most 
soluble in water should be preferred, because they would be more 
readily absorbed has been proven incorrect, for Gaglio has shoAvn 
that the insoluble salts and compounds are as well absorbed as the 
most soluble salts of the alkaloids, and that the drug is absorbed 
mostly in the intestine combined with the biliary acids and carbonic- 
acid gas. It has also been shown that if the drug is taken daily 
it accumulates in the blood up to about double the initial dose, and 
that it is eliminated through the kidneys, elimination never taking 
longer than three days, no matter how administered or what prepa¬ 
ration is administered. The least soluble preparations have been 
found the best tolerated by the stomach and intestines, because of 
their more gradual absorption, and MacGilchrist has shown that 
the acid salts are strong hemolytic agents outside the body and are, 
therefore, less safe than the neutral salts or quinine alkaloid itself. 

In the selection of the form of quinine to be used in prophylaxis 
all of the points enumerated are of importance, owing to the length 
of time that the drug must be administered. If there is serious dan- 


PROPHYLAXIS OF MALARIA. 


85 


ger of the production of hemoglobinuria by the constant administra¬ 
tion of the acid salts of quinine they should not be used; but, as a 
matter of fact, there is no evidence that the prophylactic use of any 
of the acid salts has resulted in the production of any appreciable 
amount of hemoglobinuria, so that it may be stated that they may 
be used in prophylaxis without danger. It should also be remem¬ 
bered that the proper treatment of initial malarial infections and 
of “ carriers ” of the disease are most important prophylactic meth¬ 
ods, so that the consideration of the form of quinine to be used in 
prophylaxis must not only take into consideration what form can be 
used most successfully in preventing the disease, but also what form 
is most efficient in curing those already infected. 

Of the many salts and compounds of quinine that have been used 
in the prophylaxis and treatment of malaria I believe that, from a 
military standpoint, the only ones deserving of consideration are the 
sulphate, the dihydrochloride, tannate of quinine, and the quinine 
alkaloid. Of these the sulphate and the dihydrochloride (hydro- 
chlorsulphas) are on the supply table, and, in my opinion, are all that 
are needed in the prophylaxis and treatment of malaria in the Army, 
although for prophylactic use the tannate might be adopted with 
benefit. 

This is the salt that has been so successfully used in Italy in the 
prophylaxis of the disease and which Cell! regards as the ideal one 
for this purpose, owing to the fact that it is almost tasteless, is well 
tolerated by the stomach, is absorbed more slowly, and is more com¬ 
pletely oxidized than other salts of the drug. For the treatment of 
those already infected it is inferior to the sulphate or dihydrochlo¬ 
ride. MacGilchrist 44 has recently urged the adoption, both for pro¬ 
phylaxis and treatment, of the amorphous precipitated quinine base 
or alkaloid for the following reasons: 1. It is sparingly soluble in 
water and almost tasteless. 2. Absorption is as quick and complete 
as after the administration of quinine salts. 3. Being pure quinine 
it represents quinine in the smallest bulk and weight. I. Being non¬ 
hemolytic it is safer. 5. Low cost. If further experience shows that 
these contentions are correct it would appear as though quinine alka¬ 
loid possesses advantages over salts of the drug, but experience has 
shown that the sulphate of quinine can be relied upon in prophylaxis 
and treatment in the military service, and there would seem to be no 
great advantage to be gained by carrying on the supply table sev¬ 
eral preparations of the drug. So far as the danger of the sulphate 
producing hemoglobinuria is concerned, the statistics of the Army 
demonstrate that it is infinitesimal, for despite the immense amount 
of this salt that has been used in the prophylaxis and treatment of 
malaria among our soldiers since 1898, hemoglobinuria has been so 
rare as to be a medical curiosity. 


86 


PROPHYLAXIS OF MALARIA. 


Methods of administration and dosage .—In discussing this ques¬ 
tion two problems must be considered, i. e., the best method of admin¬ 
istration of quinine to prevent infection and the dose required and 
the best method of curing initial infections and carriers of the disease. 
The latter will be discussed under a separate heading, and I will here 
give the various methods of quinine prophylaxis that are intended to 
directly protect the individual from infection by the plasmodia. 

All methods of quinine prophylaxis may be divided into two 
classes—i. e., those in which the drug is administered daily and 
those in which the drug is administered at larger intervals. The 
latter methods are all aimed at doing away with the irksome 
daily administration, but all have the fault that one must remem- 
ber the days upon which quinine should be given, with the result that 
many doses are missed, while there is good evidence showing that 
none of them are as effective in prophylaxis as the daily administra¬ 
tion of the drug. 

The following are the chief methods of using quinine as a prophy¬ 
lactic, together with the doses advocated: 

Celli’s method .—The daily administration to adults of 40 centi¬ 
grams (6 grains) of quinine, 20 centigrams in the morning and 20 
centigrams in the evening. To children, 20 centigrams (3 grains), 
10 centigrams in the morning and 10 centigrams in the evening. 

Sergent's method .—The administration in one dose, daily, of 20 
centigrams (3 grains) of quinine. 

Zieman and Nocht's method .—The administration of 1 gram (15 
grains) of quinine every fourth day, given in 0.25-gram (4-grain) 
doses. 

Plehn's method .—The administration of 1 gram of quinine (15 
grains) every seventh day. 

Koch's method .—The administration of 1 gram (gr. xv) every 
sixth and seventh, seventh and eighth, eighth and ninth, or ninth 
and tenth days, according to the severity of the infections present. 

While our choice of the exact method of giving quinine as a pro¬ 
phylactic will be influenced in the military service by local conditions, 
I believe that the method of Celli, supported as it is by years of 
success in practice, will be found the most efficient one for adoption 
by troops campaigning in a malarial country. The giving of the 
drug in morning and evening doses would probably often have to be 
replaced by the practice of giving the entire amount in one evening 
dose, but the daily administration of the drug I believe to be essen¬ 
tial to the success of malarial prophylaxis in an army in the field. 
For such service, then, I would recommend the administration of 
40 centigrams (6 grains) of quinine sulphate to every soldier every 
clay , preferably in an equal morning and evening dose, but if this is 
impracticable, in a single dose at evening. 


PROPHYLAXIS OF MALARIA. 


87 


In regard to malaria prophylaxis in semipermanent camps and 
permanent posts, the daily administration of the drug in the dose 
indicated, with the proper reductions in dose in women and children, 
will likewise be found the most efficient method: but if for any rea- 

V 

son this method can not be adopted, the administration of 1 gram 
(15 grains) on the evening of every third day should be preferred 
to any other of the interrupted methods of quinine prophylaxis. 
The reason for this is evident. It has been shown that all of the 
quinine taken at any one time is entirely eliminated within 72 hours, 
so that if an interrupted method of giving the drug is adopted it 
should be one in which there is no time when the blood is entirely 
free, and this can only be accomplished by selecting one in which 
the dose is repeated within 72 hours. While with the method advo¬ 
cated there will be a period of an hour or so in which the blood is 
free from quinine, this can be disregarded in practice. This method 
has the advantage also that it is easier to remember to take the dose 
of quinine every other day than at the fourth, ninth, and other days 
required by some of the methods of quinine prophylaxis already 
mentioned. The more simple we make our methods of prophylaxis 
the better they will succeed, especially with soldiers, and for this 
reason I do not favor the complicated methods advocated by some 
authorities in which quinine is to be taken at irregular intervals. 
The two methods outlined here will be found efficient in practice, 
the choice, if possible, resting with the daily administration of the 
drug. 

The administration of smaller doses of quinine than those advo¬ 
cated in the prophylaxis of malaria should be discontinued both 
because smaller doses are inefficient and because if there is any danger 
of the production of quinine-fast strains of the plasmodia they are 
much more apt to be produced by doses of 1 and 2 grains of quinine 
daily than by the amount recommended. Personally, I see no proof 
that such strains have ever been developed, and while the theory 
is fascinating, especially in the explanation of resistant infections 
and relapses, there is no scientific evidence that such forms of the 
plasmodia actually exist. Therefore, my objection to smaller doses 
of quinine than those mentioned is based almost entirely upon my 
conviction that such doses are insufficient to prevent infection and 
are practically useless in the prophylaxis of malaria. 

It should be distinctly understood that the dosage of quinine 
recommended to prevent malarial infections in the healthy has 
nothing whatever in common with that employed in preventing 
relapses in the infected or in the treatment of “carriers” of the 
infection. These subjects will be shortly referred to, but the ex¬ 
perience of Celli, in Italy, absolutely demonstrates that quinine 


88 


PROPHYLAXIS OF MALARIA. 


given in the manner here recommended does prevent malarial infec¬ 
tions, although some authors, as Thomson, would have us believe 
that much larger doses are necessary. It is true that larger doses 
have to be used in the treatment of the infected, but for the pre¬ 
vention of the disease in the uninfected the doses recommended will 
be found efficient in the very great majority of instances. 

As a prophylactic quinine must be administered by the mouth. 
When given in this way it may be administered in the form of a 
solution, pills, tablets, capsules, wafers, troches, and confections. 
In the military service the solution and tablets are about the only 
practicable forms where large bodies of men are to be treated, and in 
the field the cheapest and most useful method of dispensing the 
drug is in the form of tablets containing the required dose. Now¬ 
adays excellent tablets may be obtained, but even so, the utmost care 
must be used to see that quinine is really being supplied and that the 
tablets are soluble. We are all familiar with the insoluble quinine 
tablet and pill, but at the present time the tablets upon the market 
are satisfactory in this respect and will be found efficient. 

The solution of quinine may be employed in camps and posts and 
possesses the advantage that the drug is more readily and quickly 
absorbed and there is little chance of the soldier evading the taking 
of the dose. The solution is prepared by dissolving 0.32 grams (5 
grains) of quinine sulphate in 4 c. c. (1 dram) of distilled water to 
which one drop of concentrated hydrochloric acid has been added. 
A large amount of this solution can be made up at one time, as it 
keeps well, and can then be dispensed as needed. 

In order to be effective the administration of quinine as a pro¬ 
phylactic must be under the direct personal supervision of a medical 
officer, and this duty should not be delegated to any subordinate, but 
should be considered one of the most important 'personal duties that 
the sanitary officer is called upon to perform. Many of the reported 
failures of quinine prophylaxis in troops have been due to the rele¬ 
gation of this duty to careless subordinates and their inefficient 
application of the particular method selected, with the result that 
the method has been condemned without a fair trial. 

The proper treatment of malarial infections and of “ carriers ” in 
the prophylaxis of the disease. —It is well known that after an attack 
of malarial fever lias persisted for from 8 to 10 days or more, pro¬ 
vided insufficient quinine has been given, there develop in the blood 
of the infected individual forms of the plasmodia known as gametes , 
which are capable of infecting anopheline mosquitoes, and eventually 
of rendering these insects capable of transmitting malaria to man. It 
is evident that if these forms could be prevented from developing 
mosquitoes could not become infected and malaria could not be trans¬ 
mitted. It follows, therefore, that if quinine will prevent the for- 


PROPHYLAXIS OF MALARIA. 


89 


mation of gametes , and it will, every patient presenting these forms 
in the blood is an evidence of the improper treatment of his infection 
by his physician, provided, of course, that they were not present when 
he was first seen, as the result of a latent or very mild infection. As 
a matter of fact the vast importance of the proper treatment of the 
infected in the prophylaxis of the malarial fevers has never been 
fully realized by the profession or even by officers engaged in sanita¬ 
tion in malarial regions, for there is nothing more common, in many 
such localities, than to see gamete carriers going about their daily 
occupations without having received any advice regarding treatment 
and Avholly ignorant that they are a danger to the people of the 
community in which they reside. In much of our prophylactic work 
in the military service this phase of the subject appears to have been 
entirely overlooked and it is because of their importance in the 
prophylaxis of malaria that the subjects that follow are here 
discussed. 

In any thorough campaign against the malaria fevers the dis¬ 
covery and treatment of latent infections, the treatment of gamete 
carriers, or carriers of malaria, and the proper treatment of initial 
and recurrent cases of the disease are fully as important as other 
methods of prophylaxis, and yet, until recently, these subjects have 
been looked upon as being practically outside the province of the 
sanitarian and of preventive medicine. As a matter of fact, the 
prevention of “ carriers ** of any infection and the treatment of 
those who have become carriers is one of the most important func¬ 
tion of preventive medicine, while the discovery of latent infec¬ 
tions and their treatment would logically appear to be the first step 
in the prevention of any disease. This has been found to be true 
in typhoid fever, diphtheria, entamoebic dysentery, cholera, and 
other infectious diseases and it is equally true in the malarial in¬ 
fections. 

The discovery and treatment of latent infections .—By a latent 
malarial infection we understand one in which the plasmodia may be 
demonstrated in the peripheral blood, but in which no clinical symp¬ 
toms of sufficient gravity to attract attention are observed. The 
term includes both those instances in which no definite symptoms of 
malaria have ever been observed, and those cases in which the disease 
is latent between recurrences. 

It is well known that in malarial localities a considerable propor¬ 
tion of individuals in apparently fair health are “ carriers ” of the 
plasmodia, and that the natives of these regions possess an acquired 
immunity to the usual effects of the malaria toxin, although the 
plasmodia may develop in such individuals and be demonstrable in 
the blood. It has also been shown that insufficient treatment of 


90 


PROPHYLAXIS OF MALARIA. 


malarial infections results in the production of carriers of the disease 
and that many patients discharged as cured from the hospital will 
he found to have plasmodia in their blood for long periods before a 
relapse occurs, and that many of these become efficient “ carriers ” 
of the disease owing to the development of gametes during these 
latent periods. 

Proportion of latent infections .—The proportion of latent infec¬ 
tions varies greatly in different localities as is shown by the tables 
that follow, but it may be stated that such infections occur in a 
considerable percentage of both children and adults in every region 
in which malaria is endemic to any extent, and that the discovery 
and treatment of these infections is of great importance in the pro¬ 
phylaxis of malaria in such regions. In the following tables the 
percentage of malaria in the cases recorded was determined by the 
finding of the plasmodia in the blood, which is a much more accurate 
method than the splenic index which will be discussed later. 

Koch, 45 to whom we owe practically the first observations along 
this line, concluded, from his work in Africa, that latent malarial 
infections were almost entirely confined to children, but further ob¬ 
servations have shown that latent infection is very frequent in 
adults in malarial localities, and that the true index of the prevalence 
of the disease in any region can only be determined by the examina¬ 
tion of the blood of both children and adults. The following tables 
give the results of the principal investigations in regard to the pre¬ 
valence of latent infections in the natives of malarial regions: 


Table I.— Thomas's observations in Manos, Xorth Brazil. 


Age. 

Number 

examined. 

Number 

infected. 

Percent¬ 

age. 

6 months to 2 years. 

9 

38 

51 

59 

3 

20 

28 

27 

33.3 

52.6 
54.9 

45.7 

2 years to 5 years. 

5 years to 8 years. 

8 years to 10 years. 


157 

78 

49.6 

Total. ^ . 


James, 47 in India, found the percentage of latent infection in 
native children to vary greatly in different localities. At Mian 
Mir children up to 2 years of age showed 80 per cent infected; up 
to 5 years, 66 per cent; up to 10 years, 50 per cent, while children 
older than 10 years showed no infection. At Ennur children up to 
3 years }^ears of age showed 65 per cent infected; up to 5 years, 51 
per cent; up to 10 years, 46 per cent, and up to 15 years, 16 per cent. 

At Camp Stotsenburg, in the Philippine Islands, I 48 have exam¬ 
ined the blood of 45 native adults and 180 native children, all o't 
whom at the time of examination were free from svmptons of mala- 






















PROPHYLAXIS OF MALARIA. 


91 


ria. The following table gives the results of these examinations, 
but only includes 117 of the children, as only in this number could 
I obtain the exact age. 


Table II.— Craig's observations at Camp Stotsenburg, Island of Luzon, Philip¬ 
pines. 


Age. 

Number 

examined. 

Number 

infected. 

Percent¬ 

age. 

1 to 5 years. 

40 

30 

75 

5 to 10 years. 

54 

20 

37 

10 to 15 years. 

53 

13 

24 5 

Adults... 

45 

28 

62 2 

Total. 

192 

91 

47.3 





The large percentage of adults showing latent infection in this 

locality was contrary to the reports of Koch, James, and others that 

only the children in malarial localities suffered from latent infec- 

«/ 

tion, but mv observations have since been confirmed bv numerous 

j %j %} 

observers, as is shown in the following tables: 


Table III.— Olltcig's observations in Dutch East Africa. 4 * 


Age. 

Number 

examined. 

Number 

infected. 

Percentage. 

Under 1 year. 

93 

33 

35.4 

1 year to 5 years. 

220 

83 

37.7 

5 years to 15 years. 

971 

109 

11.2 

Adults. 

650 

105 

16.1 


Total. 

1,934 

330 

17.0 



Table IV .—SoreVs observations on the Ivory Coast , Africa . 50 


Age. 


Under 1 year of age... 

1 year to 5 years. 

5 years to 15 years 
Over 15 years (adults) 

Total. 


990 


Number 

Number 

examined. 

infected. 

134 

75 

253 

141 

328 

125 

275 

110 


451 


Percentage. 


56 

56 

38 

43 


44.4 


Table V.— A. PI elm's observations in Kamerun, West Africa . 51 


Age. 


Under 2 years. 

s Between 2 and 5 years. 
Between 5 and 10 years 
Adults. 


Number 

examined. 

Number 

infected. 

Percentage. 

18 

17 

94 

26 

24 

92 

40 

34 

85 

43 

26 

60 

127 

101 

79.5 


Total 





































































92 


PROPHYLAXIS OP MALARIA. 


Table VI.— Sergent's observations in Algeria, Africa . 52 


Age. 

Number 

examined. 

Number 

infected. 

Percentage. 

1 to 5 years. 

1,316 

1,360 

933 

267 

20.2 

6 to 1 O' years. 

326 

23.9 

11 to 15 years. 

272 

29.1 

Adults... 

2,471 

722 

33.3 



Total. 

6,080 

1,587 

26,1 





In Pabna Hope found that while 922 adults showed latent infec¬ 
tion only 862 children showed the plasmodia, thus demonstrating 
that in this locality the adult latent malaria ratio was higher than 
the ratio in children. 

If we consolidate the data relating to latent malarial infection 
obtained from different localities it will be found that the percentage 
of infection varies but little in adults or children in badly infected 
localities, as is shown by the following table compiled from the 
observations of the authors quoted and from my own: 

Table VII .—Consolidated table showing the prevalence of latent malarial 

infections at various ages. 


1 to 5 years.. 
5 to 10 years. 
10 to 15 years 
Adults. 

Total.. 


Age. 

Number 

examined. 

Number 

infected. 

Percentage. 


1,684 

502 

29.8 


L645 

463 

28.1 


390 

437 

31. 4 


4^931 

1,139 

23.0 




9,650 

2,541 

26.3 





From these observations, which comprise only a few of the many 
relating to latent infections, one may gather an idea of the immense 
importance of this subject in the prophylaxis of the malarial fevers, 
where anopheline mosquitoes can not be reduced beyond a noninfec- 
tious minimum, and as this is true of the majority of places in the 
Tropics the recognition and treatment of the latent infections among 
the surrounding native population is absolutely necessary in order 
to control the disease. This was demonstrated at Camp Stotsenburg, 
where a very large part of the infection present among the troops 
was contracted from the latent infections present in the native popu¬ 
lation surrounding the post. Although the greatest precautions were 
taken regarding the abolition of the breeding places of mosquitoes 
and the use of mosquito nets in the barracks, the troops suffered 
greatly from malaria, and it was not until the examination of the 
blood of the natives in the surrounding barrios showed that prac¬ 
tically 50 per cent of them were “carriers” of the infection that the 
prevalence of malaria among the troops was fully explained. It is 
undoubtedly true that a quarantine against the little barrios in close 

































PROPHYLAXIS OF MALARIA. 


93 


proximity to this post would have very greatly reduced the amount 
of malaria among the troops at that time, as the observations upon 
the latent infections in the natives proved conclusively that much of 
the malaria existing among the troops at Camp Stotsenburg was due 
to infection received while visiting the barrios and that any efforts 
to limit the disease in the post must take this condition into account. 
It will thus be seen that latent infection among the natives in a 
country occupied by troops is a most important factor in the spread 
of malaria, and that the discovery and, if possible, the treatment 
of these infections, is necessary in the prophylaxis of the disease. 

Not only are the natives in a malarial region a source of danger 
to troops, but latent infections among the soldiers themselves furnish 
a constant menace to the health of the command. Improperly treated 
cases of the disease almost always become “ carriers ” of the infection, 
and it is just as important to recognize latent infection among the 
troops as it is among the native population. As an illustration of 
this I may mention the results of an examination of the blood of a com¬ 
pany of United States soldiers returning from the Philippine Islands 
in 1902. 

In August, 1902, Company H, Sixteenth Infantry, United States 
Army, reached San Francisco from the Philippine Islands, having 
served in the Cagayan Valley, a notoriously malarial region in those 
islands. On August 16, 1902, this company, out of a total strength 
of some 60 men, had 14 men in hospital suffering from malarial infec¬ 
tion, all having had chills since arrival in the United States. On 
account of this large proportion of sick in hospital, I believed it 
would be advisable to make a blood examination of the entire com¬ 
pany, and accordingly, on August IT and 18,1 examined the blood of 
every man on duty in Company H, with the following results: Of the 
47 men who were doing duty and were apparently in good health, I 
found that 27, or over 57 per cent, showed some form of malaria 
plasmodium in their blood. Of these 27 men, 25 were infected with 
the estivo-autumnal plasmodia and 2 with the tertian plasmo¬ 
dium. Of these men no less than 13 showed crescents or gametes , 
and were, therefore, carriers of malarial infection, while the remain¬ 
der showed the forms observed in the human life cycle of the plas¬ 
modia. It is unnecessary to discuss the importance, from a pro¬ 
phylactic standpoint, of such a body of men, should they have entered 
a territory in which anopheline mosquitoes were present but in which 
malarial infections were absent, nor is it necessary to speak of the 
importance of properly treating such infections in the prevention of 
the disease. One thing, however, should be emphasized, and that is 
that had these men been properly treated in the beginning their in¬ 
fections would have been cured and they would not have become car¬ 
riers of the disease. 


94 


PROPHYLAXIS OF MALARIA. 


Methods of recognizing latent infections .—We have two methods 
of recognizing latent malarial infections—the examination of the 
blood and the palpation of the spleen, which is generally enlarged. 
Of these methods the examination of the blood is altogether the 
most accurate, although it involves considerable labor, and for this 
reason is often neglected. The splenic index, as it is called, is often 
a valuable guide as to the prevalence of malaria in a locality, but this 
organ is enlarged from other causes than malaria, and this fact often 
renders the splenic index misleading. In addition, the enlargement 
of the spleen may simply mean past infection and does not always 
indicate that treatment is needed at the time of examination. Where 
blood examinations can not be made, the splenic index must be 
relied upon, but in the military service, when it is desired to ascer¬ 
tain the actual amount of malaria present, blood examinations of 
the natives should always be depended upon, and in the prophylaxis 
of the disease among the troops a blood examination should always 
be made before patients are returned to duty after an attack of 
malaria and in any effort to discover latent infections among the 
men. Every medical officer should be familiar with the appearance 
of the various species of malaria plasmodia in both fresh and stained 
preparations of blood, and for this reason the detailed description of 
these organisms and the methods of demonstrating them have been 
given in the opening chapter of this contribution. It is true that 
much time and patience is required in making an estimate of latent 
infection in a native population and in discovering these infections 
in the men of a command, but the importance of the procedure is so 
great that it is time well expended, and the labor involved is no ex¬ 
cuse for the neglect of this very valuable prophylactic measure. 

The treatment of latent infections. —Immediately upon the dis¬ 
covery of latent infections treatment should be commenced, and the 
treatment will vary with the particular species of plasmodium pres¬ 
ent, and whether gametes have developed. The treatment of the lat¬ 
ter class of cases will be considered in the following section dealing 
with “ carriers ” of malaria, as it differs widely from that necessary 
in those individuals in whom only the forms of plasmodia concerned 
in the human cycle of development are present, comprising approxi¬ 
mately 50 per cent of all latent infections. 

The proper treatment of the class of cases just referred to is im¬ 
perative if one wishes to prevent the development of gametes , for in 
the vast majority of such cases it is only a question of time before 
they will become u carriers ” of the disease, for while gamete forma¬ 
tion may be delayed it undoubtedly occurs at some time in the vast 
majority of latent infections, as has been repeatedly shown by blood 
examinations in individual cases. Fortunatelv, these infections, be- 
fore the formation of gametes , are even more amenable to treatment 


PROPHYLAXIS OF MALARIA. 


95 


than acute infections, and I believe that I am safe in stating that 
every one of them can be cured if properly treated. 

So far as prophylaxis is concerned, the object of treatment in 
latent infections in which only the forms of plasmodia belonging to 
the human life cycle occur, is to prevent the individuals harboring 
these forms from becoming carriers of malaria, as they will be if 
gametes are allowed to develop. As these individuals are not infec¬ 
tive to mosquitoes, because gametes have not yet developed, there is 
no necessity for isolating and screening them, and as they present 
no symptoms the treatment may be pursued while they are attending 
to their ordinary avocations. In the case of soldiers it is not neces¬ 
sary to relieve them from duty, provided arrangements can be made 
for them to receive treatment at stated intervals under the direct 
supervision of a medical officer, so that* the treatment of these infec¬ 
tions need not interfere materially with military duties nor seriously 
deplete the strength of the command. It goes without saying that 
the discovery and treatment of latent malarial infection, so far as 
the military service is concerned, must be confined to semipermanent 
camps and permanent posts, as these measures would be imprac¬ 
ticable in active service in the field where protection from malaria 
must depend upon quinine prophylaxis, the use of the mosquito net, 
and other measures for protecting the men from the bites of these* 
insects. 

While in civil life the treatment of latent infections due to the 
tertian and quartan plasmodia differs from that of infections due 
to the estivo-autumnal plasmodia, in that smaller doses of quinine 
are used for the former infections, it will be better in the military 
service to adopt a scheme of treatment that will cure all cases and 
that can be easilv remembered by the individuals concerned. The 
following treatment of latent infections in which gametes are not 
present in the blood , while it may err upon the side of slightly too 
much quinine in the case of tertian and quartan malaria will be 
found efficient in infections due to the estivo-autumnal plasmodia. It 
should therefore be adopted if a single rule of treatment of all latent 
cases is to be followed, and this would appear to be the ideal method 
in the case of troops. This method of treatment is as follows: 

Every individual showing plasmodia in the blood (unless gametes 
are present) should receive 2 grams (gr. 30) of quinine daily until 
the plasmodia have disappeared from the peripheral blood. In most 
instances this will occur within three or at most four days. After 
the plasmodia have disappeared quinine should be given in daily 
doses of 1 gram (grs. xv) for two weeks, and for two weeks there¬ 
after a daily dose of 0.65 gram (grs. x) should be administered. 
After this the usual prophylactic dose of 0.40 gram (grs. vi) should 
be given daily for at least two months. 


96 


PROPHYLAXIS OF MALARIA. 


The method of administration as regards time will often depend 
upon military necessities, but it is best to give the quinine on retir¬ 
ing, or if it can be arranged the larger doses may be divided into 
equal morning and evening portions. The method may be easily 
remembered if stated as follows: Thirty grains of quinine daily 
until the plasmodia disappear, 15 grains daily for two weeks, 10 
grains daily for two weeks, and 6 grains daily for two months. 

If this method of treating these infections be faithfully carried 
out, it will be found that latent malaria will disappear and that none 
of the cases will become gamete carriers unless these forms of the 
plasmodia develop within a day or two of commencing treatment, 
when the treatment to be advised for destroying these forms should 
be adopted. 

The time to treat latent malarial infection is before the develop¬ 
ment of gametes because these forms are very much more resistant 
to quinine than are the forms concerned in the human life cycle and 
because the isolation and screening of the infected individual is 
necessary while treatment is being pursued if gametes are present. 
Any considerable number of gamete carriers in a military post is a 
reflection upon the treatment of malaria adopted by the responsible 
medical officer, and is proof positive of the improper treatment of 
acute and latent malarial infections. 

The treatment of u carriers ” in the prophylaxis of malaria .—One 
of the most important, and yet one of the most neglected, prophy¬ 
lactic measures against the spread of malarial infection is the dis¬ 
covery and treatment of “ carriers ” of the disease. It has already 
been stated that after a malarial infection has persisted for from 
8 to 10 or more days in man, forms of the plasmodia develop that 
are capable of further development in the mosquito, and that these 
eventually render this insect infective to man. These forms are 
called “ gametes " and they can easily be detected in the blood by 
microscopic examination. It is obvious that if these gamete carriers 
can be discovered and the gametes killed, these individuals will cease 
to be infectious to the mosquito; but despite this knowledge, this most 
important method of preventing malaria has been all but neglected, 
even in the military service. It has been shown that the gamete car¬ 
riers can be rendered harmless by proper treatment with quinine 
and that it is feasible to employ the drug in this way as a prophy¬ 
lactic against the disease. 

Discovery of gamete carriers. —The treatment of gamete carriers, 
.or carriers of the malarial infections, depends upon their discovery, 
and this depends entirely upon the examination of the blood of in¬ 
dividuals residing in malarial localities. The control of the treat¬ 
ment of acute and recurrent infections by frequent examination of 


PROPHYLAXIS OF MALARIA. 


97 


the blood will prevent their being discharged from hospital before the 
gametes , if present, are reduced to a noninfectious minimum, but 
there are many individuals in malarial regions who are gamete car¬ 
riers and who have never suffered from marked symptoms of malarial 
disease. Therefore it is necessary not only to control the treatment 
of acute infections by blood examinations, but to examine the blood 
of the apparently healthy if we wish to discover all gamete carriers 
and render them harmless. 

The time of occurrence of gametes. —It is universally admitted 
that gametes do not develop in patients who have been properly 
treated with quinine, and that in untreated cases they do not develop 
until the infection has presisted for several days. The length of 
time required for the development of the gametes of the estivo- 
autumnal plasmodia varies from 8 to 15 days, the usual period being 
about 12 davs. In other words, an estivo-autumnal infection must 
have persisted for nearly two weeks before we can expect to find the 
crescents, or gametes , in the peripheral blood. The gametes of the 
tertian and quartan plasmodia appear in the peripheral blood of 
man in from 7 to 10 days after the onset of definite symptoms of 
infection. j 

Although the time given is based upon the appearance of the' 
gametes after symptoms are noted, it should be remembered that 
these forms are often found in individuals who have never shown 
marked symptoms of infection, and we may find these forms pres¬ 
ent on what appears to be the very first day of an obvious infection. 

However, in the vast majority of patients, gametes do not appear 
in the blood until several days after the appearance of definite 
symptoms of malaria, and this fact is of great importance in the 
prophylaxis of the disease, for proper treatment will prevent their 
development and thus prevent the infection of the mosquito. The 
fact is also of significance in explaining the origin of these forms, 
and would appear to indicate that gametes are not introduced into 
man by the mosquito, but that, as Schaudinn believed, they are dif¬ 
ferentiated during the human life cycle of the plasmodia as the 
result of the reaction of the human organism to the parasites, and 
certainly all the evidence we possess points to this conclusion. 

The percentage of individuals showing gametes .—As only those 
individuals in whom the sexual forms, or gametes , occur are capable 
of infecting the mosquito, and thus, indirectly, of infecting man, 
it is of interest to know how large a percentage of our malarial 
patients become “ carriers." It may be stated at once, that unless 
properly treated, practically 80 per cent will probably become capa¬ 
ble of infecting the mosquito, but the statistics here given are based 
upon actual observations. 

58000°—14-7 



98 


PROPHYLAXIS OP MALARIA. 


The number of malarial patients becoming “carriers” Avill vary, 
of course, in different localities, owing to conditions favoring the 
persistence of the infection, the type of infection present, the thor¬ 
oughness with which treatment is carried out, and perhaps other 
conditions with which we are yet unfamiliar. This subject has 
been most carefullv studied in the estivo-autumnal infections, and 
the data Ave possess sIioav beyond question that the percentage varies 
greatly and that the incidence of gametes in the peripheral blood 
can not be taken as a true index of their actual occurrence in the 
body, for in many instances it has been demonstrated that blood 
obtained by splenic puncture was rich in gametes Avhen none could 
be demonstrated in the peripheral blood. In my own experience 
gametes have been observed in a little over 33 per cent of all the 
cases of estivo-autumnal malaria Avhose blood I have examined, but 
I am convinced that a longer search in the majority of these patients 
would have considerably increased this percentage. In the instances 
of recurrent infections in Filipinos, Avhich I have had the oppor¬ 
tunity of studying, crescents occurred in fully 80 per cent and were 
as numerous in the adult Filipino as in the children. Most of these 
cases had received little or no treatment, and for this reason, I be¬ 
lieve, the percentage is practically what would be observed in un¬ 
treated individuals. From my own observations, I belieA^e that at 
least this percentage of cases of estivo-autumnal malaria will be¬ 
come “carriers” unless they are properly treated. 

We possess but little data regarding the percentage of patients in¬ 
fected with the tertian and quartan plasmodia in Avhom gametes de¬ 
velop, but, in my OAvn experience, I have found that these forms occur 
in about 50 per cent of the cases of infection admitted to hospital 
and in about 30 per cent of latent infections. 

For practical purposes, an individual who does not show gametes 
in the peripheral blood must be considered as incapable of transmit¬ 
ting infection to the mosquito, but this conclusion should not be ar¬ 
rived at from a cursory examination of the blood but onty after the 
most careful examination of at least two specimens, taken at different 
times, and, if possible, on different days, for these forms are often 
numerous in the peripheral blood at one time and practically absent 
at another. 

Estimation of the number of gametes in prophylaxis .—The ob- 
seiwations of Darling and Thomson have shown that a certain num¬ 
ber of gametes must be present in the peripheral blood in order to 
render the infected individual infective to the mosquito. In a very 
ingenious series of experiments Darling 53 arrived at the conclusion 
that the peripheral blood must contain at least 12 crescents per cubic 
centimeter, or more than 1 per 500 leucocytes , in order to be infective 
to the mosquito, and that patients whose blood contains this number 


PROPHYLAXIS OF MALARIA. 


99 


as gamete-carriers and kept in hospital until, by 
the administration of quinine, the number is reduced below this mini¬ 
mum. d he number of gametes present is easily ascertained by com¬ 
paring the number with the number of leucocytes counted in a stained 
smear, properly prepared, and while there may be numerous theo¬ 
retical objections to this method of estimating the number actually 
present, I believe that the rule is a safe one to follow in prophylactic 
work, and that if it were faithfully followed it would result in a 
great reduction in the amount of malaria in any locality. 

The effect of quinine upon the gametes. —No morphological changes 
have been noted by myself in fully developed gametes of any of the 
species of malarial plasmodia after the administration of quinine, 
and the observations of Marchiafava, Gualdi, Martirano, Darling, 
and others, have shown that these forms are capable of development 
in the mosquito, even though this drug has been administered for 
weeks in large doses. Therefore the consensus of opinion at the 
present time is that after the gametes of the various species of 
plasmodia are fully developed quinine has no action upon them, so 
far as rendering them incapable of developing in the mosquito. 
This is not true, however, in the early intracorpuscular stages of the 
development of the gametes , for I have observed marked changes in 
their staining reactions after the administration of quinine which 
lead me to believe that this drug is capable of injuring them and 
probably of entirely preventing their development. 

The observations of Darling 54 and Thomson 55 have shown that 
the administration of large doses of quinine, continued over a period 
of about three weeks, will result in the reduction of the number of 
gametes in the peripheral blood to a noninfectious minimum, i. e., 
to less than 1 to 500 leucocytes, and, according to Thomson, to less 
than 1 per cubic centimeter. This reduction is considered by Thom¬ 
son to be due to the destruction of the asexual parasites from which 
the crescents arise, but I am of the opinion that it is due to the 
destruction of the gametes themselves, during their early intra¬ 
corpuscular stages of development, for reasons already noted. 

The treatment of gamete earners in prophylaxis. —The importance, 
from a prophylactic standpoint, of rendering gamete carriers harm¬ 
less, is self-evident, and the researches of the observers mentioned 
have shown us how this may be accomplished. No patient suffering 
from malaria should be returned to duty until a microscopical exami¬ 
nation of the blood shows that gametes are absent, or at least are 
present in numbers smaller than 1 to every 500 leucocytes. If these 
forms are present in a larger number than this, it is necessary to 
continue quinine in large doses, and both Darling and Thomson, as 
the result of their very careful observations, state that the drug 
should be given in doses of 2 grams (grs. xxx) per day for about 


100 


PROPHYLAXIS OF MALARIA. 


three weeks before one can expect to reduce the number of gametes 
to a safe margin in the majority of cases they have observed. Of 
course the dosage may be reduced if the gametes are present in small 
numbers, and Thomson recommends a daily dose of 1.3 grams (grs. 
xx) for the same period of time in such cases. 

The same treatment should be given the gamete carriers dis¬ 
covered in making a malarial survey and in whom the infection is 
latent. In the case of troops, every soldier, who is not in hospital and 
who shows gametes in his blood, should be placed there at once, 
carefully screened, and treated with quinine in the dosage recom¬ 
mended until his blood shows less than 1 gamete per 500 leucocytes. 
There is no other alternative than the thorough treatment of these 
“carriers” in camps and posts where anophelines can not be elimi¬ 
nated, and the only way to treat them is to confine them in a screened 
room and to give quinine in large doses until the blood examination 
shows that it is safe for them to return to duty. If allowed at 
liberty, these men furnish a constant source of infection to the re¬ 
mainder of the garrison and render other prophylactic measures less 
useful than they otherwise would be. 

The treatment of gamete carriers must be controlled by the fre¬ 
quent microscopic examination of the blood, as in no other way can 
we be sure when the patient is ready to be returned to duty. Here, 
again, we see the absolute necessity of every sanitary officer being* 
familiar with the use of the microscope in the diagnosis of malaria 
and of the morphology of the plasmodia and the methods of demon¬ 
strating them. 

The treatment of initial and recurrent infections in prophylaxis .— 
In the preceding discussion of gamete carriers it has been shown that 
the gametes do not develop until the infection has lasted for several 
days; that after they do develop, the patient becomes a “ carrier ” of 
malaria; and that in order to render him harmless he must be put 
upon sick report, confined in a screened room, and given large doses 
of quinine for practically three weeks. This is absolutely necessary 
from a prophylactic standpoint, but a still more important pro¬ 
phylactic measure is to so treat malarial infections that the gametes 
do not develop. Every gamete carrier is an evidence of either im¬ 
proper treatment or of no treatment, and if of improper treatment, 
an evidence of ignorance or carelessness on the part of the attending 
physician. In other words, the proper treatment of the initial at¬ 
tack of malaria would have prevented the formation of gametes , 
and there would have been no “ carrier ” of the disease. In the 
prophylaxis of malaria the proper treatment of acute infections is 
of vast importance, an importance that has not been realized by 
the profession, and it is sad, but true, that a very large proportion 
of the malaria present in the majority of localities is directly due 


PROPHYLAXIS OF MALARIA. 


101 


to the improper treatment of infections coming under the direct 
care of the practitioner. The practice of regarding a malarial in¬ 
fection as cured because the symptoms have disappeared is respon¬ 
sible for most recurrences and for the development of “ malaria car- 
riers,' ? and it is too often the case that a patient is allowed to resume 
his work without a blood examination having been made or anv 
directions given regarding the continued use of quinine. Despite 
the fact that the malarial infections have occupied the attention 
of the medical profession since the time of Hippocrates, it is not 
even now impressed with the fact that every such infection is re¬ 
sistant to treatment; that the disappearance of symptoms is no proof 
that the plasmodia are destroyed; and that a continued course of 
quinine is absolutely necessary to eradicate even the mildest malarial 
infection. 

The attitude in this respect is very similar to that which obtained 
in regard to the cure of syphilis prior to the use of the Wassermann 
test. In both malaria and syphilis specific drugs were known, and if. 
after the use of these drugs, the symptoms disappeared, the patient 
was regarded as cured. In the case of syphilis, however, it was 
recognized that eAen though symptoms disappeared, from two to 
three years of constant treatment was necessary before this supposed 
cure was really accomplished; but in the case of malaria a large 
proportion of the profession appear to believe that a few doses of 
quinine, if followed by the disappearance of acute symptoms, signi¬ 
fies the cure of the infection. As a matter of fact, quinine in the 
treatment of malaria is like mercury in the treatment of syphilis, in 
that its use must be persisted in for a considerable time after the 
symptoms of infection have been conquered if one desires to really 
cure the infection. When this fact is actually realized and acted 
upon by the medical profession we will witness a great reduction of 
malaria, because the “carriers” of the disease will be prevented. 
The time to begin malarial prophylaxis is with the treatment of every 
aeute infection , and if this is well done one has performed one of 
the most important duties, from a prophylactic standpoint, that falls 
to the lot of the physician. In civil life it may often be impossible 
to thoroughly treat malarial infections, but in the military service, 
owing to the absolute control the authorities have over the personel, 
the proper treatment of malaria is possible and there can hardly be 
any excuse for its neglect. 

The first requisite to the proper treatment of malarial infection is 
a correct diagnosis, and, in the military service, this should always be 
made by the aid of the microscope. This may be impossible in the 
field and the patient may have to be placed at once upon quinine, 


102 


PROPHYLAXIS OF MALARIA. 


but in camps and posts the microscope should be depended upon in 
the diagnosis of malarial fevers. In this way the exact species 
of plasmodium is ascertained and there can be no doubt of the cor¬ 
rectness of the diagnosis. 

Not onty should the diagnosis of malarial infection be made by 
blood examinations, but the treatment of the disease should always 
be controlled by frequent microscopic examinations of the blood, 
and no patient should be allowed to leave the hospital until his blood 
is free from parasites, except where a military emergency exists 
justifying such action. If this rule be followed the danger from 
“ carriers ” of the infection will be very greatly reduced and the 
surgeon can not be charged with helping along malarial disease by 
discharging “carriers” from the hospital, while gametes are still 
in the peripheral blood. If only the forms concerned in the human 
life cycle of the plasmodia are present in the blood, it will be found 
that they will disappear within a few days after beginning quinine, 
and then the patient may be returned to duty with directions regard- 
in further treatmentbut if gametes are present it will mean from 
two to three weeks of treatment with the dosage of quinine already 
recommended before they will be reduced to a noninfectious mini¬ 
mum, and the patient can be safely returned to duty. 

The treatment of initial and recurrent attacks of malarial fever 
varies with the species of plasmodium present, the tertian and quar¬ 
tan infections requiring less quinine to cure them than the estivo- 
autumnal infections. It is not my intention to discuss the treatment 
of malaria here further than to call attention to the method I have 
found effective in the usual acute and recurrent infections observed 
in hospital, the reader being referred to the many excellent works 
upon this subject for information regarding the treatment of per¬ 
nicious infections. The object of all treatment is to rid the blood 
of plasmodia as quickly as possible and to cure the disease, and I 
am no believer in routine methods in the treatment of infections vary¬ 
ing so much in severity as do the malarial fevers. It should be dis¬ 
tinctly understood that the methods that follow are merely those that 
I have found most useful in the vast majority of infections that I 
have had under personal observation and are inserted merely for the 
purpose of demonstrating the absolute necessity of continued treat¬ 
ment with quinine and of suggesting the way in which the drug may 
be employed to secure the end aimed at. i. e., the cure of the infection 
and the prevention of “ gamete carriers.” 

Tertian and quartan malaria .—In these infections, during the acute 
symptoms, quinine should be given in doses of at least 0.32 gm. (gr. 
v) every four hours until from one to two grams are given in the^d 
hours (gr. xv to xxx), according to the severity of the symptoms, and 


PROPHYLAXIS OF MALARIA. 


103 


this dosage continued until the symptoms have disappeared and plas- 
modia can no longer be detected in the peripheral blood. Thereafter 
the drug should be continued for at lease three months, the dosage 
being gradually reduced during the first two weeks of convalescence 
until the patient takes 0.40 gm. (gr. vi) per day at the end of the 
second week, and this dose should be continued for at least two weeks 
longer, and the same dose given twice a week until three months have 
elapsed from the date of attack. In regions where reinfection is 
probable, the prophylactic dose of 0.40 gm. (gr. vi) daily, should be 
adopted at the end of two weeks after the plasmodia have disappeared 
and kept up as long as required. 

/Estiva-autumnal malaria .—In sestivo-autumnal malaria the dosage 
of quinine must be somewhat increased, as these infections are more 
resistant to treatment than tertian and quartan infections. In most 
cases a dose of 0.32 gm. (gr. v) administered every four hours will 
result in the disappearance of the symptoms within three or four 
days, but not infrequently cases will be observed that require larger 
doses. After the symptoms have disappeared 1 gram (gr. xv) should 
be taken daily for two weeks, and for two weeks thereafter 0.65 gm. 
(gr. x) should be the daily dose. At the end of this period 0.32 gm. 
(gr. vi) should be taken daily for at least two months, and as long 
as required if quinine prophylaxis is necessary. 

Patients should only be returned to duty when the peripheral 
blood is free from plasmodia, or, if gametes are present, when they do 
not number more than 1 to every 500 leucocytes. Before leaving hos¬ 
pital a malaria register should be prepared for each patient, giving 
the type of infection, the amount of quinine administered, and other 
data that may be useful or necessary, and upon this register should 
be entered further treatment after return to duty. Patients should 
not be allowed to take quinine away with them for self-administra¬ 
tion, but should be instructed to report to the hospital at the proper 
time and the administration of the drug personally attended to by 
the medical officer in charge of this work. In case of transfer to 
another organization, the “ malaria registershould be sent to the 
surgeon of that organization and the treatment continued at the 
man’s new station. In this w T ay every malarial patient treated in 
the Army can be followed and a really scientific prophylaxis of the 
disease, so far as he is individually concerned, be rendered possible. 

The results of quinine prophylaxis .—In concluding this chapter 
it may be of interest to give a very few illustrations of the efficacy 
of the quinine prophylaxis of malaria where other methods have 
failed or have been only partially successful. Without question the 
most notable instance of quinine prophylaxis is that which has been 
in operation in Italy since 1905 under the auspices of the Society for 


104 


PROPHYLAXIS OF MALARIA. 


the Study of Malaria in Italy, led by Celli. In that country quinine 
is sold by the State to those able to purchase and distributed free 
to those unable, and Celli claims that since the gratuitous distribu¬ 
tion of quinine by the Government the mortality from malaria in 
Italy has diminished over 75 per cent and the morbidity in propor¬ 
tion. While other methods of prophylaxis, as screening and drain¬ 
age, have been used, Celli regards the prophylactic use of quinine 
as altogether the most efficient, and believes that it is the only 
method that can be relied upon in Italy to control malaria. In view 
of the great importance of his work I shall give a brief resume of 
the results obtained and his commentaries upon them. 

In the following table Celli 56 gives the results of quinine prophy¬ 
laxis in the army, in which the morbidity has been reduced from 
27.4 per cent to about 5 per cent by the use of this method: 

Table YIII .—Malaria in tlic Army. 


Year. 

Number 
of men. 

Number 
of cases 
(percent). 

Relapses. 

Initial 

attacks. 

Remarks. 

1902. 

199,253 
206,468 
210,637 

27.44 

21.41 

6.03 

No quinine. 
Quinine begun. 

1903. 

24.14 

17.85 

6. 28 

1904. 

19.21 

12.71 

6.50 

1905 . 

218,409 

21.52 

13.04 

8.48 


1906. 

211,245 
202,320 
216,679 
228,951 
234,104 

IS. 99 

12.67 

6.32 

Quinine. 

Do. 

1907. 

12.46 

7.96 

4.50 

1908. 

S. 04 

5.19 

2.85 

L>0. 

1909 . 

6.96 

4.72 

2.24 

Do. 

1910 . 

5.10 

3.23 

1.87 

Do. 

1911. 

233^517 

4.90 

3.04 

1.86 

Do. 




From this table it will be noted that there has been a steady reduc¬ 
tion in the number of initial attacks and the number of recurrent 
cases of malaria in the Italian army ever since the adoption of pro¬ 
phylactic quinine, in 1903, until at the end of 1911 the percentage 
of cases of malaria in the entire army was only 4.9 per cent, and this 
despite the fact that the troops were often stationed in the most 
malarious parts of the country. 

Celli 57 gives the results of quinine prophylaxis in the penal colony 
of Castiades in the following table: 


Table IX. — Malaria in the penal colony of Castiades , Sardinia. 


Year. 

Popula¬ 

tion. 

Quinine 
used, in 
kilograms. 

Num¬ 
ber of 
cases. 

Per cent. 

Remarks. 

1904. 

748 

None. 

694 

92 

No quinine. 

1905. 

861 

13,674 

731 

84 

Little quinine. 

1906. 

807 

15,080 

390 

48 

Quinine. 

1907. 

795 

40,230 

132 

16 

Daily quinine distributed. 

1908. 

700 

35, 400 

97 

13 

Do. 

1909. 

691 

32,000 

64 

9 

Do. 

1910. 

655 

15,280 

139 

19 

Only curative quinine. 

1911. 

540 

25,360 

37 

6 

Prophylactic quinine. 

















































PROPHYLAXIS OF MALARIA. 


105 


In regard to this really remarkable reduction in the number of 
cases of malaria among the prisoners in this institution from 92 
per cent to G per cent, Celli says: 

It was the prophylactic administration of quinine alone that produced the 
miracle of diminishing malaria to 8 or 9 per cent. 

In the whole of Italy the mortality from malaria has decreased 
from 21,000 deaths in 1887 to about 3,000 in 1908, quinine pro¬ 
phylaxis having been established about 1905, and Celli says: 

Beyond doubt the greatest and most persistent decrease of mortality from 
malaria in Italy was due to the increased consumption of quinine. 

In view of these results it is useless for the opponents of quinine 
prophylaxis to claim that it is of little value in the prevention of 
malarial infections, for they absolutely demonstrate that the method, 
if faithfully followed, is of the very greatest service, and similar 
results have been obtained by other observers. 

In the Dutch Indies, Bisdom 59 has reduced the percentage of 
Europeans infected from 80 to 20 per cent, and the percentage of 
infections in natives from 71 to less than 17 per cent, by the use of 
quinine in prophylaxis and treatment, and states that the use of this 
drug has been the most important factor in diminishing the inci¬ 
dence of malaria in the Netherland Indies. In Corsica, 60 Leger has 
found quinine prophylaxis very effective, the blood index among the 
inhabitants of Casabianca, for example, falling from 42,85 per cent 
to 7.14 per cent after the exhibition of 0.20 gram of quinine daily, 
and the Sergents 61 have reported excellent results in Algeria. 

The impression that quinine prophylaxis must extend throughout 
the year in malarial regions is erroneous, for in almost every locality 
there is a malarial season, and it is only just prior to and during this 
period of seasonal prevalence that it is necessary to use the drug in 
this manner. Prophylaxis with quinine should be begun about a 
month before the malarial season begins and continued for about 
the same time after it ends. In some localities, of course, the drug 
will have to be given the greater part of the year, but in most places 
it will be found that it can be omitted for weeks, or even months, 
with advantage. 

In conclusion, it may be stated that in quinine prophylaxis we 
possess a most valuable method of preventing malarial infections, 
and one that can be easily applied in the military service, but it 
should not be used to the exclusion of the more permanent methods 
depending upon the destruction of the mosquito,where such methods 
can be instituted. Although, as Celli says, 62 “those who take 
quinine daily, having a certain quantity of it in the circulating 
blood, can fearlessly subject themselves to the inoculation of blood 


106 


PROPHYLAXIS OF MALARIA. 


loaded with hamiosporidia, and, with much less danger, to the biting 
of infected anopheles," the method requires the most careful super¬ 
vision, is more or less disagreeable to the individual, and is less per¬ 
manent than the abolition of breeding places of the insects transmit¬ 
ting the disease. In the military service its greatest use will be 
found in the protection of troops in active operations in the field 
in malarial regions, and as an aid in the prophylaxis of the disease 
in camps and posts in conjunction with the other prophylactic 
measures described. 


Chapter VI. 


THE APPLICATION OF THE METHODS OF MALARIA PROPHYLAXIS 

TO THE MILITARY SERVICE. 

In the following chapter a brief summary will be given of the 
methods of malaria prophylaxis which have been discussed and the 
manner in which they may be utilized in the prevention of the dis¬ 
ease in the military service. The fact that troops are under strict 
discipline makes it possible to more thoroughly apply prophylactic 
measures in the Army than is often the case in civil life, and for this 
reason better results may be expected when such measures are faith¬ 
fully and intelligently carried out. The great reduction in malaria 
in the Army already noted is proof of this statement, and there is 
no reason why these infections should not be still further reduced, 
and eventually disappear in our permanent posts if prophylactic 
measures are continued. 

As has already been stated, the prophylaxis of malaria requires 
very different methods in the field than in semipermanent camps and 
permanent posts, and in all situations the methods employed will 
vary according to local conditions and military exigencies. This 
fact must be recognized by every practical sanitarian, and in the 
following discussion regarding the application of malaria prophy¬ 
laxis to the military service it should be remembered that the sug¬ 
gestions offered are merely suggestions, which may or may not be 
practical in actual seiwice owing to the peculiar conditions surround¬ 
ing each prophylactic problem. 

Malaria prophylaxis in the -field .—The necessity for malaria pro¬ 
phylaxis in the field during the active operations of an army should 
have been ascertained before the invasion of the country with which 
hostilities are being conducted. This presupposes the accurate map¬ 
ping of the country from a sanitary standpoint, a hitherto much 
neglected branch of military information. In the past an accurate 
knowledge of malarial localities would have saved many armies an 
enormous loss from this cause, as campaigns could have been planned 
so as to avoid exposing troops to these infections, and the most ex¬ 
haustive knowledge of terrain is of little use if troops are so deci¬ 
mated by malarial infection as to be unable to take advantage of such 
knowledge. An accurate sanitary map showing the prevalence of 
disease in the country to be invaded would be of great value in the 
planning of any campaign, as in the majority of instances it would 
be found that badly infected districts could be avoided without dam- 

107 


108 


PROPHYLAXIS OF MALARIA. 


age to the campaign from the military point of view, or prophylactic 
measures could be instituted in time and prevent the infection of the 
Army. 

In active operations in the field we must depend for the preven¬ 
tion of malaria upon the prophylactic use of quinine and the use 
of the mosquito net. Quinine sulphate should be given in daily 
doses of not less than 10 centigrams (gr. vi), preferably adminis¬ 
tered in 20 centigram doses morning and evening. In many and 
perhaps the majority of instances it may be found that the entire 
dose must be given at one time, and if so it is best to give it in the 
evening. The men should be assembled at a convenient time and 
the quinine administered by a medical officer, care being taken to see 
that each soldier swallows his dose. The quinine may be most con¬ 
veniently carried and dispensed in tablet form, but the utmost care 
should be taken to see that the tablets are readily soluble. 

If acute attacks of malaria develop in the command it will be 
found best to send the men disabled to the nearest field hospital, 
where the type of infection can be ascertained and properly treated, 
or, if necessary, the patient may be sent to the base hospital for 
treatment. After the plasmodia have disappeared from the blood 
the men may be returned to duty, but not before. Nothing will be 
gained by keeping men suffering from acute attacks of malarial 
fever with an advancing column, as they will only encumber it and 
may prove a source of infection to their companions. 

In all regions in which mosquitoes occur the Yedder mosquito net 
should be used in the shelter and other tents, and inspections should 
be made by medical officers in order to see that the net is being prop¬ 
erly used. Guards should wear head nets and gloves, and both the 
mosquito nets and head nets should be inspected frequently for tears 
or holes and promptly repaired. 

It is believed that with an efficient enforcement of the use of nets 
and of prophylactic quinine an army will be able to campaign in the 
most baclty infected malarial districts without suffering very greatly 
from the infection. These methods will not prevent all infection, but 
may certainly be trusted to prevent the vast number of infections 
which would otherwise occur, and which, in times past, have ren¬ 
dered entire armies useless as fighting machines. If such methods 
had been efficiently carried out at Santiago it is safe to say that 
malaria would not have placed our Army in such a position that 
retreat was actuallv considered. 

Malaria prophylaxis in semipermanent camps .—The first and 
best step in the prevention of malaria in camps of short duration is 
the selection of a region free from malaria as the camp site. Here 
again the value of a map showing such regions is evident, but in its 
absence, and, if time and military contingencies permit, much may be 


PROPHYLAXIS OP MALARIA. 


109 


learned in a short time by observations of the kind of mosquitoes 
present, the location of their breeding places, and an examination of 
the blood of from 20 to 40 children and adults in the region being 
investigated. This entire study of a location need not consume more 
than a few hours and will generally result in definite knowledge 
regarding the prevalence of malarial infection. If, despite the pres¬ 
ence of infection, the locality must be selected for a camp site, the 
measures pursued will vary, of course, with the length of time the 
camp is to be occupied and the facilities afforded for their execution. 

If the camp is to be occupied for only a few days, the prophylactic 
use of quinine, the use of the mosquito net, and the clearing of an 
area from 100 to 200 yards around the camp of long grass and under¬ 
brush will be about all that can be done in the way of prevention. 

In the case of camps that will probably last for several months and 
are, therefore, of semipermanent character, the same precautions 
should be taken regarding the selection of a site as recommended for 
permanent posts, and similar prophylactic measures should be em¬ 
ployed if malarial infection appears. 

Malaria prophylaxis in permanent posts .—Before establishing a. 
permanent military post in the tropics or in regions in which the 
presence of malarial infection is suspected, a malaria survey of the 
locality is of the greatest importance, and, in most instances can be 
made without interfering with military movements. If such sur¬ 
veys had been made before certain posts were established in the 
Philippines, it is probable that other localities would have been se¬ 
lected with a resultant saving in money and efficiency. Certainly 
there can be no excuse for establishing a military post in a very 
malarious region when a malaria survey would have shown that 
adjacent regions were free from the infection and when there was no 
military necessity for occupying exactly the locality chosen. 

The following points should be considered in estimating the safety 
of a locality as regards malaria when the question of choosing it for 
the site of a post is considered: The statistics regarding fevers in 
the locality, if there are any, should be studied; the character of the 
soil and the nature of the terrain; the species of mosquitoes present; 
the breeding places of mosquitoes and the kind of larvae present; the 
presence and number of infected mosquitoes; and the number of 
latent infections in children and adults. A map of the locality should 


be obtained, or prepared, and the entire region districted, after which 
a careful investigation regarding the points mentioned should be 
made of each district by a trained medical officer. Upon the map 
should be marked the location of breeding places of mosquitoes, the 
species found in each breedery, and whether any of the insects 
examined were found infected with plasmodia. In addition the 
dwellings of individuals found infected with malaria during the 


110 


PROPHYLAXIS OF MALARIA. 


blood examinations of the inhabitants should be indicated on the 
map, thus showing the relation of breeding places to such infections. 
The map should also show the ratio of infected individuals and 
mosquitoes and the most severely infected districts. The work of a 
few days in the examination of the blood of the inhabitants, the dis¬ 
section and examination of mosquitoes, and the location of breeding 
places of anophelines will result in a most valuable mass of data, 
enabling one to judge of the advisability of locating a post in the 
region investigated, and what methods would be best adapted to 
ridding the region of malarial infection. Such a malaria survey is 
just as important to the future health of the command as the ques¬ 
tion of an adequate and pure water supply. 

In posts that are known to be malarial the prophylactic methods 
adopted must vary with local conditions, and the best way to become 
acquainted with these conditions is to make a malaria survey, just 
as one would in deciding upon the location of a site for a permanent 
post. The post should be districted upon a map and a most careful 
search made for the breeding places of mosquitoes, while, coinci- 
dently, the species of mosquitoes present should be ascertained and 
the ratio of infected insects. An examination of the blood of at 
least 40 adults and children living in the immediate vicinity of the 
post should be made, as well as of the same number of soldiers in the 
post, in order to ascertain the presence of latent infection, and the 
records of the post should be consulted as to the prevalence of 
malaria during the past. As soon as this preliminary survey is 
completed one will have data upon which to work out the best 
method or methods of prophylaxis for the particular locality investi¬ 
gated. While in rare instances it will be found that mosquitoes 
can be exterminated and that this is the only prophylactic measure 
that need be adopted, in the vast majority of posts the malarial prob¬ 
lem is best attacked by using all the methods at our command. 
These consist in the abolition of the breeding places of mosquitoes 
and their destruction in the adult stage by trapping and catching 
by hand, the protection of the command from their bites by screen¬ 
ing and the use of nets, and the destruction of the plasmoclia by 
quinine. The latter method may be omitted, so far as the healthy 
population is concerned, provided malarial infection is not very 
intense and the other methods mentioned will control the situation, 
but in badly infected posts, where it is impossible to get rid of mos¬ 
quitoes, quinine prophylaxis should be adopted during the malarial 
season. 

Every elfort should be made to rid the post and the surrounding 
country for a distance of at least 2 miles of breeding places of 
anophelines. Very often the most that can be done is to reduce their 
number, owing to the immense cost of drainage and filling in, but as 


PROPHYLAXIS OP MALARIA. 


Ill 


much should be done as possible, however gloomy the outlook. If 
mosquitoes are very numerous they can be greatly reduced by mos¬ 
quito traps and by detailing men for the purpose of catching the 
insects by hand, as is done in the Canal Zone, where this method 
lias met with really remarkable success. 

It is unnecessary to state that every post in which anophelmes can 
not be eradicated and where malaria prevails should be thoroughly 
screened, and vet the cost of this procedure has prohibited its adop¬ 
tion in some of the most malarious posts occupied by the Army, 
until quite recently. The economy which forced the omission of this 
very important prophylactic measure was in reality an extravagance, 
for the loss of time and money occasioned by the malarial infections 
in the troops was much more costly in the end than the amount in¬ 
volved in the purchase of proper screening material. Barracks, 
quarters, and other buildings should be screened with the best copper 
netting of not less than 16 meshes to the linear inch, and, where the 
yellow-fever mosquito is present, of 18 meshes to the linear inch. 

The use of the mosquito net for the bunk should be rigidly en¬ 
forced unless quarters and barracks are screened, and a nightly in¬ 
spection should be made to see that the men are using the nets 
properly. The head net and gloves should be worn by soldiers on 
duty in the late afternoon and during the night in all posts where 
malaria is prevalent to any extent. 

All shelter for mosquitoes in the post and for a distance of 300 
yards outside the post limits should be reduced to the minimum, and 
the utmost care should be taken that no small breeding places, such 
as are furnished by unused hoppers, rain barrels, tin cans, and small 
pools due to improper drainage, exist in the post. 

The prophylactic use of quinine should be enforced if malaria is 
prevalent enough to warrant it, and daily doses of 0.10 centigrams 
(gr. vi) should be administered under the personal observation of a 
medical officer. In most posts in which malaria occurs this will not 
be found essential in the control of malaria, if “ earners ” be dis¬ 
covered and treated and all acute and recurrent cases of malaria be 
kept in hospital until the plasmodia disappear from the blood under 
quinine and if treatment be continued in the manner already de¬ 
scribed. In the Tropics, however, where the soldiery is continually 
coming in contact with a badly infected native population, the use of 
quinine prophylaxis should be insisted upon during the malarial 
season. 

If natives in whom there is a large percentage of latent infection 
and many “ carriers ” live around the post, it would be an economical 
measure for the Government to issue them free quinine, to be dis¬ 
tributed and administered by a medical officer. In many instances 
this measure alone would practically eliminate malaria from among 


112 


PROPHYLAXIS OF MALARIA. 


the troops, because it would remove the greatest source of infection 
of mosquitoes and, indirectly, of the command. 

The discovery and treatment of latent malarial infections and of 
“carriers” in the command is a most important prophylactic duty, 
which should never be neglected in posts where the disease is preva¬ 
lent. This involves, of course, the microscopical examination of the 
blood of all members of the command, and, in badly infected regions, 
this examination may have to be repeated at monthly intervals, 
although the prophylactic use of quinine should render this unneces- 
sarv after the first examination has been made. In a large command 
such an examination may be impracticable, but in smaller posts the 
measure is practical and, although it involves a great deal of work, 
should be followed out where malaria is really a serious problem. 

Every patient admitted to hospital for malaria should have the 
diagnosis confirmed by the microscope, if possible, and treatment 
should be controlled by a daily examination of the blood. No patient 
should be discharged from the hospital until the peripheral blood 
is free from plasmodia except in the case of gamete carriers, who 
may be returned to duty when the gametes are reduced to less than 
1 to 500 leucocytes. 

A “ malaria register ” should be prepared for every patient, upon 
which should be entered the type of infection, the treatment given in 
hospital and ordered after leaving the hospital, the date when the 
plasmodia disappeared from the blood, the date of return to duty, 
and any other information that may be thought desirable. When 
transferred to another command, the malaria register should be sent 
to the surgeon of the post, who can then continue the treatment. 

Every patient returned to duty should be directed to report at a 
certain time for quinine in continuance of the treatment, and the qui¬ 
nine should be administered under the personal supervision of a 
medical officer, if possible. The time of reporting can be so arranged 
as to be convenient for all concerned, and each dose administered 
should be entered upon the man’s “ malaria register.” 

When soldiers suffering from latent malarial infections are dis¬ 
covered they should be placed in hospital and a most careful exami¬ 
nation be made relative to the presence of gametes in their blood. 
If gametes' are not present, they should be returned to duty as soon 
as the blood is free from plasmodia, with directions to report for fur¬ 
ther treatment; but if gametes are present, the patients should be 
treated in hospital until the gametes are reduced to less than 1 per 
500 leucocytes. The method of treating these cases has already been 
discussed in Chapter V. A “ malaria register ” should be prepared 
for these cases and used in the same manner as for acute and recur¬ 
rent infections, but the fact that the case is a latent one should be 
entered upon the register. 


PROPHYLAXIS OF MALARIA. 


113 


The suggestions given above for the prophylaxis of malaria in 
the field, in temporary camps, and in permanent posts, do not cover 
all that may be done along this line, but may serve as a guide in the 
prevention of these infections in the military service. The aim of 
the medical officer should be to do all in his power to prevent the 
transmission of these infections, but the methods to be adopted will 
vary, of course, with special conditions, and it will often be possible 
to control the disease without resorting to all of the methods that 
have been described. However little he may be able to do in the 
way of eradicating mosquitoes, he has absolute control over patients 
in hospital, and can see that no man who has been in the hospital for 
malaria is returned to duty until he has ceased to be a source of 
danger to his companions. He can also insist upon the continuance 
of quinine until there is a reasonable surety that the infection is 
cured, and thus prevent the recurrences which furnish the majority 
of malarial cases in any hospital. 

In conclusion, it may be stated that the malarial fevers are en¬ 
tirely preventable and their presence, to any extent, in an army 
post is a reflection either upon the intelligence of the sanitary officer 
in control, or upon that of other authorities who, either by indiffer¬ 
ence to the recommendations of the sanitary officer or unwillingness 
to supply the necessary funds, have rendered the efforts at prophy¬ 
laxis futile. 

REFERENCES. 

1. Laveran, A. Note sur un nouveau parasite, etc. Bull, de l’Acad. des 

sciences. Paris. Ses. 20th Feb., 18S0. 

2. Ross, R. The role of the mosquito in the evolution of the malarial para¬ 

site. The Lancet. 1898. II. p. 488. 

.°>. Laveran, A. Ibid. 

4. Craig, Chas. F. Classification of the malarial plasmodia. Boston Med. 

and Surg. Jour. 1909. CLX. p. 677. 

5. Theobald, V. V. Monograph culickhe of the world. 6 vols. 1901 to 1902. 

British Museum. 

6. Howard, L. O.; Dyar, H. G.; Knab, F. The mosquitoes of North and Cen¬ 

tral America and the West Indies. 1. 1912. Carnegie Institution. 

7. Ludlow, C. S. Disease bearing mosquitoes of North and Central America, 

the West Indies, and the Philippine Islands. Bull. IV. 1913. Surg. 

Gen. Office, War Dept. 

8. Darling, S. T. Studies in relation to malaria. 1910. Dept. San. Isthmian 

Canal Commission, p. 22. 

9. Beyer, G.; Pothier, O. L.; Couret, M ; and Leman. Bionomics, etc. Rep. 

Mos. Com. to Orleans Parish Med. Soc.. New Orleans Med. Jour. 1902. 

54. p. 419. 

10. Kinosliita, K. Ueber Verbreitung der Anophelen auf Formosa, etc. Arch. 

f. Schiffs- und Tropenhyg. 1906. N. pp. 621-676, 708-741. 

11. Nuttall. G. II. F., and Shipley, A. E. Studies in relation to malaria. II. 

jour. Hyg. 1901-1903. 1, p. 45-269; 451. 2, p. 58; 3, p. 166. 

58000°—14-8 



114 


PROPHYLAXIS OF MALARIA. 


12. Stephens, ,T. W. W., and Christophers, S. It. Malaria in an Indian canton¬ 

ment. Rep. Malaria Comm. Royal Soc. 1003. p. 22. 

13. Ludlow, C. S. Ibid. 

14. Hurst. The pupal stage of Culex. Studies from Owens College, Manchester. 

1890. 2. p. 47. 

15. Chagas. Zeitschr. f. Infectionskrank Hygiene. 1908. 60. p. 321. 

16. Smith. Rep. New Jersey State Agri. Exper. Station. 1004. Trenton. 482 

pp. 

17. Howard, L. O. Ibid. 

IS. Craig, Chas. F. The malarial fevers, luemoglobinuric fever, and the blood 
protozoa of man. 1900. p. 60. 

10. James. Malaria in India. Scient. Mem. Officers Med. and San. Depts. 
Govt, of India. 1002. 

20. Gorgas, W. C. Rep. Dept. Sanitation. Isth. Canal Commission. 1913. 

p. 46. 

21. Le Prince, J. A. Recent progress in antimalaria work, etc. Trans. XV. In- 

ternatl. Cong. Hyg. and Demog.. Washington. 1013. V. p. 545. 

22. Watson, M. Prevention of malaria in the Federated Malay States, p 952. 

p. 2S2. 

23. Lutz. Waldmosquitos und Waldmalaria. Centralbl. f. Bakt.. 1903, Abt. 

33. p. 282. 

24. Nuttall. Influence of color upon anopheles. Brit. Med. Jour. 2. 1901. 

p. 668. 

25. Kulagin. Zur Naturgeschichte der Mticken. Zool. Anzeiger. 1907. 31. 

p. S65. 

26. Le Prince, J. A. Mosquito destruction in the Tropics. J. Am. Med. Assoc. 

1008. LI. p. 2204. 

27. Le Prince, J. A. Ibid. p. 2206. 

2S. Howard, L. O. An experiment against mosquitoes. Insect life. 1893. V. 
p. 12, 109. 

29. Darling, S. T. A mosquito larvicide, etc. Am. Jour. Public Health. 1912. 

February. 

30. Orenstein, A. J. Mosquito catching in dwellings in the prophylaxis of 

malaria. Am. Jour. Public Health. 1913. 3. p. 106. 

31. Darling, S. T. Studies in relation to malaria. Isth. Canal Com. 1910. 

p. 32. 

32. Craig, Chas. F. The malarial fevers, haemoglobinuric fever and the blood 

protozoa of man. 1909. p. 354. 

33. Guiteras. Report to Col. J. II. Kean, U. S. Army Med. Corps quoted in 

Howard's The mosquitoes of North and Central America, etc. 1912. 
Washington, p. 363. 

34. Darling, S. T. Ibid. p. 31. 

35. Report of Surgeon General of Army. 1912. p. 147. 

36. Howard, L. O. The mosquitoes of North and Central America, etc. Wash¬ 

ington. 1912. p. 367. 

37. Procaccini. Ricerche profilat. centri le malaria, etc., Annali. di Medicina 

Navale. 1900. xi. p. 14. 

38. Tzuzuki, J. Malaria und lire vermittler in Japan. Arch. f. Schiffs u 

Tropenhyg. 1902 . 6. p. 285. 

39. Orenstein, A. J. Screening as an antimalaria measure. Proc. Canal Zone 

Med. Assoc. 1912. v. Part I. p. 12. 

40. Craig, Chas. F. Studies in the morphology of the malarial plasmodia 

after the administration of quinine, etc. Jour. Infec. Dis. 1910. 7. 

p. 285. 


PROPHYLAXIS OF MALARIA. 


115 


41. Rieux, J. Mode d’Action de la quinine stir Plasmodium vivax , etc. Bull. Soc. 

Path. Exot. 1013. 6. p. 153. 

42. Billet, A. Action de la quinine sur les lnematozoaires de paludisme. Bull. 

Soc. Path. Exot. 1913. 6. p. 330. 

43. Janies, W. A. Personal communication. 

44. MacGilchrist, A. C. Pharmacological action and uses of quinine. Proced. 

Third Meeting Gen. Malaria Committee. Nov. 18. p. 17. Simla. Gov’t 
Press. 

45. Koch, It. Zweiter bericht uber die thatigken des malariaexpeditio. Deutsch. 

Med. Wochenschr. 1000. 5. p. 88. 

46. Thomas, H. IV. The sanitary conditions and diseases in Manaos, etc. 

Ann. Trop. Med. and Hyg. 1910. iv. p. 7. 

47. James. Scientific mem. officers med, and sail, depts. Govt. India. 1902. 

N. S. No. 2. 

48. Craig, Chas. F. Observations upon malaria. Latent infections in natives of 

Philippine Islands. Phil. Jour. Sci. 1906. I. p. 523. 

49. Ollwig, R. Zeitschr. f. hygiene u infectionskrank. 1903. 45. p. 345. 

50. Sorel, F. Le paludisme a la cote d’Ivoire. Bull. d. la Soc. Path. Exot. 

1912. x. p. 365. 

51. Plehn, A. Die acuten infectionskrankheiten bei den negern, etc. Virchow’s 

Archiv. 1903. Supplement. 

52. Sergent, Edmund and Etienne. Atti. della soc. per gli studi della malaria. 

1909. x. p. 217. 

53. Darling, S. T. Ibid. 

54. Darling. S. T. Ibid. 

55. Thomson, D. The destruction of crescents. Ann. Trop. Med. and Parasit. 

1912. 6. p. 223. 

56. Celli, A. The restriction of malaria in Italy. Trans. XV Internatl. Cong. 

Hyg. and Demog. 1913. v. p. 526. 

57. Idem. Ibid. p. 528. 

58. Idem. Ibid. p. 525. 

59. Bisdom. W. Einige bemerkungen uber die malaria im indischen beer in 

den Jahren, 1895-1909. Janus. 1912. 17. p. 400. 

60. Leger, M. Le paludisme en corse. Pub. de l’lnst. Pasteur. 1913. Laval. 

61. Sergent, Edmond and Etienne. Etudes epidemiologiques et prophylactiques 

du paludisme. Ann. Inst. Pasteur. 1913. 27. p. 373. 

62. Celli, A. The restriction of malaria in Italy. Trans. XV Inter. Cong. 

Hyg. and Demog. 1913. v. p. 522. 

MONOCxROPHS UPON THE MALARIAL FEVERS. 

1895. Thayer and Hewetson. The malarial fevers of Baltimore. 

1897. Thayer, IV. S. Lectures upon the malarial fevers. New York. 

1900. Marchiafava and Bignami. Malaria. Twentieth century practice. New 

York. Vol. XIX. 

1901. Craig, Chas. F. The aestivo-autumnal malarial fevers. New York. 

1904. Stephens and Christophers. Practical study of malaria. London. 

1905. Zieman, H. Malaria. Handbuch der tropenkrankheiten. Mense. Leipzig. 
1909. Craig. Chas. F. The malarial fevers, haemoglobinuric fever, and the 

blood protozoa of man. New York. 

1913. Ruge, R. Malariaparasiten. Handbuch der pathogenen microorganismen. 
2nd auflage. BDVII. 


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